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Full text of "Television Engineers Pocket Book"

TELEVISION 

ENGINEERS' 

POCKET BOOK 



THIRD EDITION 



Editor: 



J. R Hawker 



TELEVISION ENGINEERS' 
POCKET BOOK 






Edited by 
I. P. HAWKER 

Much new information has been added to the 
enlarged and fully revised third edition of this 
pocket manual and data book, specially designed 
to meet the everyday practical needs of all con- 
cerned with the repair and maintenance of 
modern television receivers. 

Apart from essential reference data on 
cathode-ray tubes, valves, television stations and 
transmission standards, there are extensive sec- 
tions on the basic circuits used in receivers, on 
fault finding — including a new trouble tracing 
chart — and on the alignment of Band 1/1 1 i re- 
ceivers. There is guidance on the conversion of 
Band I sets and a comprehensive list of receiver 
intermediate frequencies. Colour and transis- 
torized receivers are described. 

There are also special sections on servicing 
equipment, dealing with printed-circuit models 
and projection receivers, aerials and interfer- 
ence problems. 

Both the experienced engineer and the new- 
comer to service work will find this handy book 
invaluable for on-the-spot repairs, as well as a 
most useful addition to his workshop library. 

Third Edition 

A companion volume to "Radio Servicing Pocket 
Book". 






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NET 






TELEVISION ENGINEERS' 
POCKET BOOK 



Books of Allied Interest 

RADIO SERVICING POCKET HOOK 
Editors: E. Motley and J. P. I lawker 

RADIO AND TELEVISION ENGINEERS' REFERENCE ROOK 
hdttor; J. P. Hawker. Advisory Editor: W. E. Pannctt, A.M.I. E.E, 

PUBLIC ADDRESS AND SOUND DISTRIBUTION HANDBOOK 
Advisory Editor: A.J. Walker 

TELEVISION AND RADAR ENCYCLOPAEDIA 

Edited by W. MacLanaehan 

FREQUENCY-MODULATED RADIO 
by K. R. Snirley, Ph.D.. M.I. E.E. 

HIGH FIDELITY SOUND REPRODUCTION 
Editor: E. Molloy 

INTROIH'CTION TO HI-FI 
by Clement Brown 

DICTIONARY OF ELECTRONICS 

by Harley Carter, A. M.I. E.E. 



TELEVISION ENGINEERS' 
POCKET BOOK 



EDITED BY 



J. P. HAWKER 



Specialist Contributors 

D. H. FISHER, A.M.I.E.E. 

F. LIVINGSTON HOGG, M.BRIT. I.R.E., A.M.I.E.E 

E. C. HOWELL, M.BRIT.I.R.E., A.LE.E. 
T. B. SMARTT 

A. G. THOMSON, B.SC.(eNG-), A.M.I.E.E. 



LONDON 

GEORGE NEWNES LIMITED 

TOWER HOUSE, SOUTHAMPTON STREET 
STRAND. W.C.2 



© George Nenmes, Ltd. 
1954, 1958, 1900 



First published 
Second edition 
Third edition 



1954 
1958 

mon 



Printed in Great Britain by Richard Clay and Company, Ltd. 
Bungay, Suffolk 



PREFACE 

Since this pocket manual and data book on television servicing 
was first published, the establishment of the I.T.A. network on 
Band III has brought about considerable changes in receiver 
technique. This new and enlarged edition has therefore been 
extensively revised to take these and ether recent developments 
fully into account and to provide, in a handy-sized book, the 
most practical possible summary of basic facts and technical 
data for day-to-day reference. 

In addition to a wealth of useful reference data and information 
on transmission standards, it contains practical hints on installing, 
fault -tracing and aligning domestic equipment, together with 
notes on many special testing instruments introduced during tbe 
past few years to facilitate this work ; aerial equipment for local 
and " fringe " reception ; matching devices; receiver intermediate 
frequencies; and maps of the main B.B.C. and I.T.A. service 
areas. Informative sections are devoted to: interference causes 
and cures; valve and picture tube data, pin connection and 
equivalents tables; colour television; colour codes; Band ill 
conversions; printed circuits; projection systems; and the basic 
circuitry used in modorn receivers. 

J. A. Ki;i'i'iiiuii;i! 
J. P. Hawker 



NOTE TO TlllKD EDITION 

Tins new edition has again been enlarged and much fresh material 
ami ilnia added. Their arc new .sections on colour anil tran- 
sistorised receivers while the sections on basic circuitry and fault 
finding have been revised and expanded: all data sections — 
including station lists, intermediate frequencies, cathode-ray 
tubes and valves — have been brought fully tip-to-date. 



CONTENTS 
Section 

1 Standards and Waveforms . 

Scanning — British transmission standards — Syn- 
chronisation pulses — -Transmitter band-width. 

2 British Tele vision- Network . 

Frequencies and station** — Field -strength maps — 
I.T.A. — Programme companies Location of sta- 
tions. 



Page 
9 



1(3 



Basic ( 'ihcI'ITUY ...... 

Typical receiver K.K. stages mid timer units 

I.F. stages Detector and Video Amplifier So I 

Channel — V.H.K.K.M. reception. Tin h- kis.'s 
Sync, separation Power supplies Automatic pic- 
ture control Flywheel sync- Typieul Circuits. 



20 



Co i.'u 'it Tki.evi.siun ...... 

Sequential systems — N.T.S.C. systems Tri-colom 
picture tubes — Subjective colour systems — Experi- 
mental receiver. 



68 



Transistuhiseo I-5k('i;ivkks ..... 

Introductory- -Sean Diagnificatioz) Optica] nmgni- 
iieatioii syslem Transistor D.T. converters. 



74 



6 Projection Television ..... 

Schmidt optical system —Projection cathode-ray 
i uhes— Tube data — Circuitry — Adjustments. 



78 



Band III Conversions ..... 

Types of converter — Converting T.R.F. receivers — 
Patterning — Converting superhets. 



01 



Installing and Servicing Receivers . 

Field servicing — -Installation — Adjusting controls — 
Tuning signals — Servicing precautions — Servicing 

printed circuits. 

7 



!lii 



8 CONTENTS 

Section Page 

9 Servicing Equipment , . . . . ,114 

Essential equipmont— Signal generators — Multi- 
range meters — Pattern generators— Oscilloscopes — ■ 
Wobbulators — Insulation testers — Component test 
bridges— Valve testers — E.H.T. voltmeters — Signal - 
strength meters — Valve voltohmmeters — Crystal 
calibrators. 



10 Receiver Aerials ...... 130 

Basic terms — The dipole — Aerial designs — -Band 
III aerials — Feeder cables — Matching— Attenua- 
tors — Installation — Fringe equipment — " Ghosts ". 

11 Interference . . . . . .144 

Impulse and heterodyne interference: — Typical 
sources — Interference by television receivers. 

12 Fault Finding . . . . . . .152 

Component deterioration — R.F, instability — Video- 
amplifier faults — Cathode -ray tube faults — Syn- 
chronisation faults — E.H.T. faults — Time-base 
fault;* Li m.' output transformers Turret repairs 
— Trouble-tracing chart— Miscellaneous picture 
faults, 

13 Alignment . . . . . . . .174 

Response curves — Pre-mtxer circuits — Alignmcni 
of T.R.F. receivers and I.F. stages — Use of sweep 
generator — Tuner alignment — List of inter- 
mediate frequencies. 

14 Cathode -ray Tubes . . , , . 21 J) 

Focusing and deflection — Modulation— Ions — A In - 
minisation — Handling and replacing — Picture- 
tube salvage — Correct usage — Data on commercial 
tubes — Equivalent tables — Replacements. 

15 Valve Data . . . . . . .238 

Correct usage — Heater characteristics and pin 
connections — Equivalents. 

16 Colour Cooes ....... 253 

Index ......... 250 



[SECTION 1] 

STANDARDS AND WAVEFORMS 

The basic principle of transmitting pictures over wire or radio 
circuits by breaking down a series of images into a large number 
of tiny points, or picture elements; transmitting a signal corre- 
sponding to the light value of each element; and then later 
reassembling an identical series of light points in the same 
sequence at the receiving end is now so widely understood as to 
require little detailed explanation. For practical television 
purposes, it is, however, important to appreciate that although 
the number of elements into which each picture is broken down 
provides the final measure of the definition of the picture that 
can be achieved on any given transmission system, a number of 
other factors are of importance in determining the fidelity and 
picture quality of the reproduced picture. These factors include 
the band-width of the transmission channel, the amount of flicker 
that can be tolerated, the spot size of the cathode-ray -tube beam 
at the receiver, contrast, and the linearity of the deflection 
systems. 

It should be noted that, although it is usual to refer to hori- 
zontal scanning, in fact the lines are 'not precisely horizontal, 
but incline downwards as they proceed from left to right, owing 
to the influence of the frame deflection, which produces the 
second dimension of the picture. 

Picture-repetition Frequency 

The rato at which the process of scanning must bo repeated is 
determined by the following factors : the process must appear 
continuous to the eye, and must bo repeated sufficiently often 
to give tho impression of continuous movement of objects to the 
viewer, and to avoid noticeable flicker. This process depends 
for its success on the " persistence of vision " of tho human eye, 
that is to say the fact that the retina retains an impression of an 
image for an appreciable fraction of a second after the object 
itself has disappeared, A series of still images presented at a 
rate of about 10 per second will provide an illusion of continuous 
movement, but would be accompanied by considerable flicker. 
If the rate is increased to 25 per second, the flicker will be con- 
siderably reduced, but will still be noticeable, particularly 
where the picture is bright : a repetition rate of 50 per second 
will eliminate flicker for all practical purposes. 

If, however, a television system were to adopt a repetition rate 
of 50 complete pictures a second, the video frequencies involved 
in the transmission of a high-definition system would rise to an 





10 



TELEVISION ENGINEERS' POCKET BOOK 





MOVEMENT DUE TO LINE TIME BASE 



(O) 
-SCA.NXlMi 



MOVEMENT DUE TO LINE TIME BftSE 



C6 



(u) sequential; (6 Double Inteklai e. 



extremely high figure, necessitating ati excessive transmission 
band-width. Tina difficulty has led to the adoption of what is 
termed " interlaced " scanning : in this system instead of trans- 
mitting each lino of the picture in sequence, alternate lines of the 
picture am first scanned, i.e., the lines 1, 2, 3, 4, of Fig. I (6), The 
remaining even lines {A, B, 0, D, etc.) are then scaimed. By 
this means, although only 25 complete pictures are scanned each 
soeond in the British system, the frame is evenly illuminated 
50* times per second. Since, with high definition, it is difficult 
for the eye to pereeive the scanning of the individual lines, the 
offect is to raise tho repetition rate to 50 per second while at tho 
samotime keeping tho amount of detail and the video frequencies 
to those for sequential scanning at 25 frames a second. Willi tin- 
British system of 405 lines, those are divided into two frames of 
202k lines each, tho half-line playing an important role in auto- 
matically controlling tho interlaco of the receiver scanning 
system. It is important to note that whore, for any reason, tho 
control of the receiver interlaco is faulty, the scan" will tend to 
trace out two almost identical paths for both frames, and thus 
produce a picture in which the lines aro clearly visible, and to 
reduce picture quality. 

Bicture Transmission 

Before discussing the make-up of the British television wave- 
form, it is necessary to consider briefly why the transmission of 
pictures should be more complex than the transmission of sound. 

The transmission from a sound broadcasting station must bo 
capable of reproducing in tho receiver the audio frequencies 
(pitch and harmonic content) of tho programme at each moment 
and also tho intensity (amplitude) of the sound; this is done 
basically by modulating a steady radio -frequency carrier with 
dlectrical frequencies corresponding to the audio frequencies, 
and thus in effect producing a slight variation of transmitter 



STANDARDS AND WAVEFORMS 



II 



frequency in the form of sidebands, while at the same time 
varying the amplitude (voltage output) of the transmitter to 
correspond with the intensity of the sound. 

In picture transmission, since each camera-cell, unlike the 
microphone, is sensitive only to the average illumination pre- 
sented to it, and not to detail, it is necessary to indicate the 
relative brightness of each picture element in turn by means of 
scanning, and when this differs a high video frequency will 
automatically occur. Thus, as in sound broadcasting, a radio- 
frequency carrier is modulated by varying the amplitude of the 
transmitted wave, in this caso to correspond with the intensity 
oT illumination over the range black to white; and this in turn 
produces sidebands, or frequency variations, whenever a change 
in illumination tokos place. Thus, so far, vision transmission 
ia not basically different from sound transmission, except in 
the width of the sidebands, which will be much greater for vision 
l ban for sound. However, for successful picture transmission, 
it. is also necessary to provide two additional items of infomalion 
that aro not required in sound transmission; theso arc the 
lino- and frame-synchronisation signals, which aro required to 
ensure that the raster on the television-receiver screen is traced 
out exactly in step with the scanning of the transmitted image 
by tho screen. It is also desirable that the cathode-ray -tube 
trace be suppressed during the flyback periods. We thus 
have in offect a number of different types of information that must 
be radiated by means of a single radio carrier in such a way 
that each item can readily bo separated and mado to perform its 
particular function at the receiving end. 

British Television System 

The methods adopted in the British television service to con- 
voy these items of information may bo summarised as follows : 

Picture brightness or light value of each picture element is 
transmitted by amplitude modulation of the carrier, adopting a 
figure of 30 per cent of peak output to correspond with " black " 
and the full peak output to correspond with iJ peak white ". 
This is termed "positive" modulation, to distinguish it from 
the alternative system (as used in tho United States), in which 
peak output corresponds to l< black ". 

Tho video frequencies produced by tho variation of picture 
brightness levels form sidebands varying from Mc/s when 
transmitting an even tone picture (*.«., all black, all white, all 
grey, etc.) up to approximately 3 Mc,'s for a fine network of black 
and white lines. These video frequencies are separated from the 
carrier frequency by a detector or demodulator as is dono in 
sound broadcasting. 

Synchronisation is effected by using tho " blacker than black " 
portion of the carrier output, the entire output from tho trans- 
mitter being suppressed (0 per cent of peak output) for greater or 
lesser periods to provide frame and lino pulses. In the receiver 
theso pulses are separated from the vision-intensity signals by 



12 



TELEVISION ENGINEERS' POCKET BOOK 



PEAK WHITE 



SERRATED LIME 
.--REPRESENTS PICTUHfc 
DETAIL 




FRONT PORCH f'Siis) 

ALLOWS TIME FOR A 

LINE ENDING IN WHITE 

TO RETURN TO BLACK LEVEL 



LINE SYNCHRONISING 
PULSE 



■BACK PORCH (6/<i) 



Fia. 2.— Section op television Waveform showimi Link-synchronising 

Pulses. 

means of an amplitude limiter (usually termed the synchronising 
separator), and are then further separated into frame- and linc- 
triggering pulses by moans of circuits capable of distinguishing 
between pulses of different lengths, 

A section of this basic waveform is illustrated in Fig. 2. The 
time A-B represents a period of one line (98-7 pS), from which it 
will be seen that this period is made of 82<2 pS of picture informa- 
tion : a " front porch " (pedestal) pre-lino synchronising signal- 
suppression period of 0-5 ^S, to allow time for the carrier to drop 
to the black level in cases where the line ends on a point of high 
picture amplitude (i.e., white, or near white) ; this is followed by 
a 10-/iS synchronising pulse ; then a " back porch T ' or post line 
synchronising signal-suppression period of 6 /iS, to cut off tho 
cathode -ray -tube trace during tho flyback period. It should bo 
noted that in these diagrams all pulses are shown with vertical 
edges; this cannot be achieved in practice, though the leading 
and trailing edges of the pulses are extremely stoop. It is in 
fact most important that the leading edge of this pulse, which 
triggers off the line-scan generator, should retain its extremely 
steep slope in tho receiver; otherwise the timing of the scan 

Table 1.1. — British Television Standards 



Number of pictures per second 
Number of frames per picture 
Number of frames per second 

Aspect ratio (width/height) , 

Number of lines per frame . 
Number of lines per second . 
Fnterlacing .... 
Modulation 



25 

50 

: 3 (current) 

: 4 (original) 

202Jr 

10,125 

2:1 

positive 



STANDARDS AND WAVEFORMS 13 

Table 1.2. — British Synchronisation Constants 



Constant 


Approx. Time 


Time in Terms 
of Line Period 


Duration of line pulse .... 


10 ^S 


01 H 


Duration of porch preceding line pulse 


0-SuS 


0-005 H 


Duration of porch following line pulse 


005 H 


Duration of framing pulse 


39-35 uS 


0-4 H 


Space between successive framing pulses . 


10 pS 


0-1 H 


Frame suppression period 


1400 fiS 


14 H 


Frame-flyback suppression period 


1000 jiS 


10 H 


Duration of line period 


99 *iS 


in 



generator will not he accurate, and a ragged edge to the picture 
will result, 

Frame Pulses 

So far we have considered only the line-synchronisation 
pulses, but the waveform for a double- interlace system must also 
contain pulses that will trigger off the frame-scan oscillator 
twice in each complete picture : at tho end of the 405th line and 
halfway through tho 203rd line, as well as making provision for 
the suppression of the flyback trace during the return of the spot 
from the bottom of the picture to the top. The frame pulses 
take the form of 8 broad pulses of 39-35 /iS duration, each occupy - 
i ng the space of 4 lino periods as shown in Fig. 3. This is followed 
by tho suppression of picture information for a further period 
of 10 lines, to allow time for the frame flyback trace to occur; 
this is known as the post-frame synchronising suppression 
period. During this time it is necessary for line pulses to be 
inserted to maintain the line-scan oscillator at the correct fre- 
quency. A similar sequence takes place halfway through tho 
203rd line period, and picture information is not resumed until 
halfway through the 217th line. The complete sequence is 
shown in Fig. 4, (a) representing a section of the waveform 
during any period from the 15th-202nd line period or the 218th- 
405th line period ; (6) showing the sequence of frame and line 
pulses occurring at the end of the 405th line, and lasting until the 
beginning of the 15th line period of the next picture; and (c) 
showing the sequence from the commencement of the 203rd line 



END OF 
405** LINE 




EIGHT FRAME PULSES OF 39 '35 jus 
WITH IO/iS BETWEEN THEM 



innr 

PICTURE SIGNAL SUPPRESSED FOR 
EQUIVALENT OF FURTHER 10 LINES 
MAKING TOTAL NEARLY IflOOyuI 



Fig. n,— Frame-scan Waveform. 



14 



TELEVISION ENGINEERS' POCKET BOOK 



WHITE LCVEL=)0O% MODULATION 



BLiC>; LEVEL-3dfc MODULATION J 3% 
BLACKER -THAN- BLACK' LEVEL -IERO MODULAIION 




8 BROAD PULSES WHrCH POHM 'HE FRAME SYNC f>ULSE 

Fio. 4, — tarn asp frame-; pulsus. 
Table 1.3. — Comparison of Tklevtston Stand arks 



Standard 


British 


American 


li'iropmn 






(/•'.(/.('.) 


(f.cj.H.) 


Total width of channel . 


5 Mc/a 


8 Mc/s 


7 Ho/8 


Number of lines . 


406 


636 


6S6 


Interlacing . 


a : 1 


2:1 


2 : 1 


Number of lines per second . 


Ifl^M 


15,750 


16,626 


Number of pictures (frames ■) 








per second 


25 


30 


25 


Number of frames (lields •) 








per picture (frame °) 


2 


2 


2 


Number of frames (fields •) 








per second 


50 


GO 


50 


Modulation 


A.M. positive 


a.m. negative 


A.M. negative 


Ulacfe level 


30% peak 


'•>"„ peak 


75% peak 


Aspect ratio 


4 :3 


4 :3 


4 :3 


Ouster 


Qpper 


Lower 


Lower 




sideband 


sideband 


sideband 




^niijiressed 


suppressed 


suppressed 


Approx. width of vision clutn- 








nel . 


8 Mc/a 


■] Itcft 


5 Me/s 


Aerial polarisation 


\ • I'U'-ai (main) 


Rortaoata] 


Usually 




Horizontal 




horizontal 




(subsidiary) 






Sound carrier 


3-5 Mc/s below 


■1-5 Mc/s above 


5-5 Mc/s above 




v!:-.hiil earner 


vision carrier 




Sound modulation 


A.M. 


I'.M. 


i-'.M. 


1' .M. deviation (max.) . 


— 


±26 ke/s 


±50 ko/s 


P.M. pre-empbasis 


— 


75j(ri 


60 M s 



STANDARDS AND WAVEFORMS 



15 



* American terminology, 



•I 



period. It will thus bo appreciated that, although we consider 
the B.B.C. system aa having 405 lines, 28 of these lines are lost 
in so far as the transmission of picture information is concerned, 
so that in practice an enlarged viewing screen would show a 
picture made up of 376 complete and 2 half-lines. 

Band-width 

The video-frequency band-width required to transmit a tele- 
vision picture faithfully with equal vertical and horizontal 
resolution is given by the formula : 

„ , uh, N*X A X P(l - 8,) 

Band-width = 5 — -— r= «-; — 

Z X (1 — oi) 

where N is number of lines, A is aspect ratio, P number of 
pictures per second, Sp fraction of frame period occupied by 
fiMtur suppression, && fraction of line period occupied by .line 
suppression. For B.B.C. standards JV = 405, A .= i., P •= 25, 
8, = 0-069, S L = 0172 giving a theoretical band -width of 
3 06 Mc/a, 

The maximum theoretical definition is reduced iin practice i by 
deficiencies in the transmitter and receiver, and the anmunt of 
detail which can be seen is further dependent on the brightness 
and contrast in the .picture, and the distance from whiclr it.ris 
viewed. In general, the finest detail is seen in the brightest 
parts of the picture, at high contrast when viewed closely. A vcry 
bright picture may, however, cause glare and so reduce the visi- 
bility of detail. 

Methods of minimising the ill effects of room light, such as 
" black " cathode-ray-tube screens, neutral or coloured plastic 
filters and black net over the face of the tube have all been used 
moro or less successfully, and are effective because the light from 
the cathode-ray tube is attenuated only once when coming 
through the filters, whereas stray light shining on the tubo is 
reflected back through the filter and attenuated twice. 

It is interesting to note that the eye is capable of resolving 
detail about twice as fine as is observable in a high -quality 
television picture at a viewing distance of four times the picture 
height. The actual ratio varies considerably according to the 
brightness and contrast of the detail, but under no circumstances 
is the eye called upon to work at its maximum effort when looking 
at television, so that eye -strain should not result from this cause. 

It has been suggested that the correct viewing distance is the 
least at which the scanning lines are not visible. 

There may well be instances where it is not convenient to sit as 
closo as this' to the screen, and some surprise may be experienced 
at the good quality of the picture seen from a greater distance. 
Another little-understood peculiarity of vision causes small 
pictures to appear sharper than large ones for the same rolative 
viewing distance, so that sets employing large tubes should have 
special care taken to ensure the very best definition. 



[SECTION 2] 

BRITISH TELEVISION NETWORK 

The very and ultra, high frequency bands allotted in the United 
Kingdom for television and sound broadcasting are shown in 
Table 2.1. At present, Band I is used for B.B.C. television 
transmissions; Band II for the B.B.C. V.H.F./F.M. sound broad- 
easting network; Band III for the I.T.A. television transmissions. 
Experimental 405- and 625-lino television transmissions have 
been made in Bands IV and V by the B.B.C, and it seems 
likely that these bands will be used primarily for television. 

For double-sideband amplitude modulation of a 405-line 
vision transmitter it is necessary to have a bandwidth of at 
least 6 Mc/s, although the use of asymmetric sideband modula- 
tion (see later) reduces this requirement to under 5 Mc/s. Band 
I, 4'l-68 Mc/s, is divided into five transmission channels, each 
shared between a main high -power station and one or more 
lower-power stations, geographically situated to minimise tin; 
risk of interference. The division of Band I is shown in Fig. 1 , 

Table 2.1 — V.H.F./U.H.F. Broadcast and Television Bands 



Band I . 

Band 1 1 . 

umid in. 

Hand I V , 
Hand V . 



41-08 Mc/s 
87-5-111(1 Mc/s 
174-216 Mc/s 
470-585 Mc/s 
610 -SOU Mc/s 



7-3-4-4 m. 
3-4-3 m. 
17-1-4 in. 

fi-1 TjI I'm. 
43-31 cm. 



VISION 
No. 4. 



VISION 
No.S 




3-5 Mc/s 3-25 MC/ S 3-SMc /s| | 3:5 Mc/s 



i-S Mc/s 



5 Mc/s 



$ Mc/s 1-25 Mc/s 



■41 Mc/s TO 68 Mc/s 

Fig. 1 .— Ffikqukncy amxktatioxs uor the Band I THumaioN OftAtatme 

16 






BRITISH TELEVISION NETWORK 



17 




SOUTH EN D-ON- SEA 
•DART FOR DO/i-SOOUV/fll MARGATE 



uxbi 

)'0/uV/r / BE . AOlNG L,ne 
HEwauOT. Sunningdac£«^cRY5TALPAL.ACE cH^m^^T^ <*rams 

,a'siNGSTOKE» • . • REIGATE MAIDSTONE /j 



\ -~,i ,,/_ GUILDFORD 

\ SOO^uV/m #1 

^WINCHESTER , CRAWLE* 

• \ • VhaSLEMERE 

salisbur\ »^»_ • 




e-v NEWPORT 



PETERSFlELD hay war ds heath 

HOVE.. BRIGHTON ^ — *HASTII 
'EASTBOURNE 



•ASHFORp^ 

FOLKESTONE 
lOO(UV/m 
OUNGENESS 



PORTSMOUTH WORTHING 

loojuv/m 



in;. 2. I'KMvisioNAi, vm&Smomvtt contours for the b.b.c. uuystal 

1'Al.ACK 'PEIJtVISlON TllASSMITTKB. 

Beeeiving aeritil height SU ft. The contours represent, expected average values 
:irnl variations ul ;w niufh as :S : I may occur. Owing to [mull condition;;, the boun- 
ilaries are nob rigid: fading may be experienced in dink-nlt locations. 

from which it will be seen that the No. 1 channel is of sufficient 
width to accommodate a double-sideband transmission as used 
at the original Alexandra Palace station, while the remaining 
tour channels aro based on asymmetric transmission band- 
widths. In practice, all British television transmissions are now 
of the asymmetric type. 

Each sideband, taken separately, contains all tho detail of the 
modulating wave, and, as it is possible to transmit one sideband 

Table 2.2. — Frequencies of Television Transmitting 
Stations 



Channel 


Son ml, 

Mcjs 


Vision, 

Mcjs 


Channel 


Sound, 

Mr I 


Vision, 
Mtf* 


1 
2 
I 

4 

B 

Band 111 
6 


41-5 

48-25 

53-25 

58-25 

sa-es 

176-23 


45 7 

-.1-7.-, 8 
56-78 U 
IU-7.J 10 
lit;.;;) n 

12 
ITU-T.". U 


IS] -2:> 
18848 
191-88 

1D6-25 
201-25 
206-20 
211-25 


1184-75 
IK9-7.-I 
IM-7.-. 
MB-78 
204-76 

--".'• ;:. 

214-75 



18 TELEVISION ENGINEERS' POCKET BOOK 



BRITISH TELEVISION NETWORK 




I'ui. 



-AF-PIIOXIMATK nivUt-STRENQTH CnNTtlUUK nr 'i'lIK EEOUD MOSS 
TKLKV1310N TllAXSMnTKIt. 



Harrier frequency 61-75 llc/s. Receiving aerial height 30 ft. The Geld strength nt 
any given place may differ over a ranee of ±11) db from the value indicated by the 
contours, which represent average values. Considerable fading may be experienced 
in the shaded area. (The map above, and those shown oppusile, are reproduce! by 
courtesy of the B.ll.C.) 

iiiid suppress most of the other, a considerable reduction in 
band-width results. In British television practice, the lower 
sideband is used, and the corresponding sound channel is spaced 
3-0 Me/s below the vision-carrier frequency. In view of the low 
modulating frequencies, double-sideband working is retained 
for the sound transmission. Thus the complete asymmetric 
television station, with its high-fidelity sound and vision, occupies 
a channel of approximately 5 Me/s. The spacing of tho sound 
and vision carriers of any one station is 3-5 Mc/s, and the spacing 
of the vision carrier to tho next higher channel sound carrier is 
1 r. Me/s. 

Field Strengths 

Figs. 2-fi show the results of surveys of the field strength of the 
main B.B.O. television transmitters, made by the B.B.C. research 
department. In tho unshaded areas reception should be good, 
but in the shaded areas, which are considered to be outside the 
transmitter service area, satisfactory reception will depend upon 



Kins, I am> ft. -AwKoxiM.vn-: tfiKLn-sTKKXnTu OiSToms OVXBB KUtK o'Suorra 

(AHOVK) AS'll SETTON (JOI.IM7IELI) (11KLOW) TKI.KVISION '1'KAKRMITTKItA. 

Eteoatvtag awfal height 30 ft. The field strength at any given place may differ over 
a range of ± 10 db from the value indicated by the contours, which represent, average 
\ dues. L'rinsiderable fad i uc may be experienced in the shaded areas. 



Mm*vi 





, ' t v^/V^ HUM •mttii.4 f 

WQgWJg^V "v WARWICK /-*,*.• so ." r .*'* uTo "* 

&£m8s£$! mza ?" &■■■&' ■■■■ 



• •■ilia. '^8!?*' w»aws« 




."rairuhos 



20 



TELEVISION ENGINEERS' POCKET BOOK 




Table 2.3. — B.B.C. Television Transmitters 



c/ntnntl 


Station 


Polarisation 


Vision 
(*!!'.) K.U.f. 


1 


QtnW Palace 


Vertical 


200 


1 


Divls (Belfast) 


1 1 i gfawntel 


12 


1 


Thrums te r ( V> ' i a k ) 


Vcrticul 


u-a-o-8 6 


■i 


Holme Moss 


Vertical 


101) 


2 


North Hess ary Tor (S. Devon) 


Vertical 


1-18* 


2 


Uosemarkie CS. Scotland) 


lloriy.otihd 


1 


| 


Londonderry 


lluriitOlltnl 


1 


g 


Whiteliawk Hill (Brighton) 


Vertical 


0-4 max.* 


2 


Swingate (Hover) 


\ertical 


n-25-i» 


8 


Kirk .'Shotte 


Vertical 


Kin 


s 


RowridRe 


Vertical 


1-32° 


a 


Norwich 


Horizontal 


1-11)0 


3 


Blaen-Plwvf (West Wales) 


ITuriaontal 


0*5-2* 


4 


Sutton Coldiield 


Vertical 


100 


4 


Mehlnim (Aberdeen) 


Horizontal 


4-1 1* 


-1 


Saudale (Carlisle) 


Horizontal 


to 


1 


Channel Islands 


Horizontal 


O'ffl-1* 


4 


Folkestone t 


Horizontal 


iiiiiiT max, 


a 


wenvoe 


Vertical 


100 


5 


1 'onion Pike 


Horizontal 


12 


t 


llonglas, fate of Man 


Vertical 


0-7-2-S« 


5 


Peterborough 


Horizontal 


1-2 


5 


Orkney 


Vertical 


4-17° 






* Directional aerial. t T jOW power translator (■' Satellite "), 

Further low-power translator stations, to he completed by 1962, at: Rnrrow, 
JJerwick-on-1Veeil,Ennisk)[len,Kort^Wi]liani,f;a]iL«;hie]s,l])!iwidi,DlaiKlrindod Welts, 
Looh Leven, 'Oban, Oxford, Pembroke, Sheffield, 8kegn689 and West Cornwall. To 
be completed by 1304: Forfar, nrantown-on-Spcy, Lewis, Pitlochry, Shetland, Skye, 

i':ini:irviin. Ilu-liiap, St'-arhnroiu.'li anil Swindon. 






BRITISH TELEVISION NETWORK 



21 



local conditions, and fading may occur. As many television 
receivers now incorporate facilities for the reception of V.H.F./ 
I-'.M. Band II sound broadcasts, the frequencies and locations of 
B.B.C. stations are given in Table 2.4. 



Table 2.4 


—B.B.C. V.H.F./F.M 


. Stations 










Third and 




Home Programme 


Light 


" A'etitmk 


Italian, 






Programme 
Mcjs 


Three " 
Progrmiunu, 










Mejs 


Programme 




Mefs 


tiivis(N. Ireland) . 


94-5 


Northern Ireland 


■Ki-1 


93-3 


Douglas (Isle of Man) 


92-8 


Kor thorn 


SS-I 


90-6 


Holme Moss . 


9,1-7 


Northern 


s;i:; 


:\\;> 


Kirk o'SbuUs. 


M-8 


Scottish 


89- D 


92-1 


Mi-Idriini (N.K. Scotland). 


9.1-1 


Scottish 


SR-7 


!I0'9 


Norwich (Tacolncston) 


94-1 


Midland 


SVI-7 


91-9 


Peterborough . 


94-5 


Midland 


90-1 


!>2-3 


Pontop Pike . 


92-9 


Northern 


s,s-r. 


m-i 


hliindonna (Anglesev) 


111 II 


Welsh 


8U-6 


91-8 


Llangollen (N'.K. Wales) . 


93-3 


Welsh 


88-9 


•lt-1 


Koscmarkic (X. Scotland) 


94-0 


Booittsh 


89-fi 


fll-S 


Jtowridgc 


92-9 


West of England 


88-Ei 


ao-7 


S. Devon (North TfitnWHJ 










Tor) .... 


92- S 


West of England 


88-1 


M-a 


Sandale (Carlisle) . 


92-5 

'.<■(■ 7 


Scottish 
Northern 


88-1 


90- 3 


Sutton Cold Held 


92-7 


Mi.i kin. 1 


88-3 


IK)-.", 


Wenvoe. 


:ii ■:; 

H2-1 


Welsh 

West of Kngland 


xi-:t 


30-8* 


\\ est Wales (Wauii-l'l™ vfj 


'.i:;i 


\\i-\A\ 


>s-7 


90-9 


Wrotbam 


BS-S 


Ijondon 


k;h 


91 -:s 


Orkney .... 


•x;-i 


Scottish 


89-3 


in-:. 


Thninster (Wick) . 


■.ii'. 


Scottish 


90-1 


024 



Further stations, to be completed by 1962, a t : Berwk'k-on-Tweed, Channel Islands, 

Dover. Port William. Galashiels, l.londrindod Wells, 1 yocb Tjrvcii, Londonderry. Ol kin, 

Oxford and West Cornwall. To lie completed by 1944: Forfar, liraiilown-oii-^ii;. . 

. Pitlochry, Shetland, Bkye, Bast UnoobHhire, Bmifaklllen, ivmbrokcSlicllicld, 

8.W, Sootlaad. 

B.B.C. Television Translator (Satellite) Stations 

In I S158 the B.B.C. began using a new type of low-power tele- 
vision transmitter, known us a " translator ", nl Folkestone. 
This town is typical of small populated areas which are within 
or adjacent to the service areas of the main B.B.C stations, but 
ure prevented by hills from obtaining satisfactory reception. 

A translator converts tin* sound and vision transmission fre- 
quencies from one channel to another without demodulation to 
audio and video frequencies which occurs when a normal receiver 
nnd transmitter relay installation is employed. This simplifica- 
tion increases the reliability of the equipment, which can therefore 
lie arranged for automatic operation without attendant staff. 
Because the equipment is small it can conveniently be housed in 
*vi;ithor-proof and insect-proof cabinets, thus dispensing with the 
need for a station biulding. 



22 



TELEVISION ENGINEERS* POCKET BOOK 



Transatlantic Cable Transmissions 

The first transmissions of news films via the transatlantic cable 
were made by tho B.B.C. during 1959. This was done by 
vestigal -sideband modulation of a 5-ke/s currier with video in- 
formation of highly restricted band-width. The line definition 
is first reduced to about I ■"."> Mc's, then only every alternate frame 
of the 16- mm. fibn is scanned with 200-line definition by B slow- 
speed flying-spot film scanner. At the receiving end each of these 
alternate frames is reproduced as two frames. These measures, 
though they degrade the picture quality considerably, reduce 
the band-width to about 450 ke/s. This band-width is then 
reduced about. 100 times by slowing down the scanning proem, 
allowing the resulting video information bo be accommodated in 
the 4,. r »00-e/s band-width of the cable circuit. Tims, using this 
system, a fifteen second news item takes nixmt twenty-live 
minutes to transmit over the cable. 

INDEPENDENT TELEVISION AUTHORITY 
The Independent Television Authority is a public corporation 
responsible for the provision of television services. It owns and 
operates television stations, but the programmes they transmit 
arc provided by programme companies. I "ndor the Television 
Act, tho Authority is responsible for shaping, guiding and ex- 
tending independent television. Its policy is to go forward 
from the establishment of independent television in selected 
areas of dense population to tho provision of a full national 
service. 

The Authority regulates the system under which the pro- 
gramme companies sell time for advertisements. It also has 
wide responsibilities under the Television Act for securing 
proper standards in tho programmes; and it is particularly 
concerned with such matters as accuracy in news, impartiality in 

Tauijj 2.5. — I.T.A. Television Trank.mittkms 



Channel 


.•it'll'"" 


Polar'- 


IfolM 


8 


MiiUiimls 


Vertical 


■2<H) feW K.H.1'. 


8 


n.e. Bnglaad 


Horizon l al 


100 kW B.BJ». 


»• 


London 


Vertii.:il 


190 kW K.LU'. 


11 


l,;mc:i>hirr 


Vertical 


100 k\V Id t.l'. 


!l 


X. lrcliiinl 


EforfocnttaJ 


nm kW B.BJV 


e 


Devon 


Vertii :d 




1U° 


Yorkshire 


Vertical 


300 k\V K.li.F. 


If) a 


S, S.:ot,u»!id 


Vertical 


89 17.". k\\ B.H.P. 


io« 


B. Wales 


\'lTtii-;il 


•Jin) kW E.It.r. 


in 


Dover 


Vertical 


— 


11 


Idle of Wight 


Vertical 


loo k\\ B.BJ? 


11 


Hob) AaglTa 

Cornwall 


ll'ir !/.•■: ' il 


800 k\\" E.It.r. 


12 


Vertical 





• Onset. 
Bsattona tiiive also Iwen aaaaoooed for: Aberdeen ('probuolv Channel B); IScrwiuk 
Channel islanda; luveruests; Ule of Man: siohvuy (protiuldy Channel II); West 
Wales. 



BRITISH TELEVISION NETWORK 



23 



LIMIT OF FRINGE AREA 

BAN8URV" ^1 ( . . .. < 



LIMIT OF SECONDARY 
..... V SERVICE AREA / 

.■BICESTER ,- CJjLljTON 

"MLcaauarC HCRTFO>V 
■ . ./ Sr AL&ANS ■/* "T_ , ._,JS 



■COLCHESTER 



LIMIT OF 
PRIMARY 
SERVICE "» >* 

AREA READING}! 



SOUTHAMPTfim 




BASINGSTOKE • 
AN DOVER* 



WINCHESTER' 



IK:. 7. COYEIUfSK OF TifK CROYDON f.T.A. Tbassmittkk. 
Site heidlit. 373 ft., ueriol hetpht 175 ft. 

2 mV median i*ontoiir; J mV median contour; 

.... 1 mV median contour. 

matters of controversy, balance in subject matter and the 
maintenance of good taste. In these, and in all other matters, 
it maintains close and continuous contact with the programme 
companies it has appointed. 

Programme Companies for I.T.A. 

A, B.C. Television Ltd. (Midlands and North, Saturdays and 

Sundays). 
Associated-Jtediffusion Ltd. {London, Mondays to Fridays). 
Associated Television Ltd.. (London, Saturdays and Sundays; 

Midlands, Mondays to Fridays). 
(rranada TV Network Ltd. (North, Mondays to Fridays). 
Scottish Television Ltd. (Central Scotland, whole week). 
Htiiitfieru Teh H/Jtioit (Central Southern and Soutli Kastern Kiigland). 
Tijtic-Tees Television (N.E. Englnnd). 
Independent Television for South Wales dk the West of England, 

Ltd. (South Wales and West of England, whole week). 
[i't/lia. Television (East Anglia). 
' i -~.lv i- Telerifiion (Northern Ireland). 
Westward Tifi eixion (S.W. England). 
independent Television News Ltd. (Main news bulletins for all areas). 

Location of Transmitters 

London Region, Croydon ; Midland Region, Lichfield; North- 
ern Region, Wiutor Hill (Lancashire) and Emloy Moor (York- 
shire); Central Scotland Region. Black Hill; South Wales und 



24 



TELEVISION ENGINEERS' POCKET BOOK 



' V.^!"™ ,- ^ >a"rbboath 

, DUNDEE \ 



•.--">■ •CRIEFF 





LEVEN 

r ■ 

/STIRLING COWDENBEATH 

i / * ^JALLOA ■ ^KIRKCALDY 

/ / ^x • DUNFEBMLINE 

(IHELENSSURGH, 



NORTH BERWICK 
DUNBAR 



BLACK HILL 



t ft #>>-Cr-*P UMBARTON *" » EDINBURGH 

M7^E«i3»- * •bathcateT^^ 

S \ ',| I PAISLEY* J^^PW f . 

V, \ VlABCS ^T • UOTHEBWELL I y-^ 

^i / DALRY CARSTAIBS I ,/ 

\ «V STBATHAVEN_ • ) ^ r €„. r * S 



y 




7 



BERWICK^ 

UPON 
TWEED 



GALASHIELS 

* •REL50 



TROON 
PRE ST WICK, 






flu. s.— estimated ai'pkoximate covhhaue ok Tin: Soorasfl I.T.A. 

TELEVISION TlUXsMITTKU. 

Site height 800 16., mean aerial height 1.B50 It. 




■ e rtvv/m 



KlU. 9. — Kstimatkii Oovi-'JIAGK RF THB NoiiTNHKS I.T.A, TliANSMlTTKKiJ, 
WlNTKK II 11.1, (LAKCASHIKK) AM) EllLEY MOOK (i'DllKSlIIKK). 



BRITISH TELEVISION NETWORK 

D WARRINGTON 



25 



■ SHEFFIELD 



BUXTON 



■CHESTER 



CREWE ■• ," 



• /STOKE-ON -TRENT 
•I 
• I 

. v 



„.• STAFFORD! 

SHREWSBURY ■ 

" YlIN< 




oGRANTIIAM 



LICHFIELD 

/ WELLINGTON ^ 



DERBYa 

■ BURToH-OM-TR*ENT 

LEICESTER \» B rjAKHAM 



WOLVERHAMPTON I 



KIDDERMINSTER ■ 





HEREFORD 



GLOUCESTER ■ 



WALSALL 
■ BIRMINGHAM 

COVENTRY ■ 

■"RUGBY,"' 

■ LEAMINGTON SPA „ T „ k% 

V J J •^NORTHAMPTON 

STRATFORD ^fA-AVOf I 

j^"" ■••■•* 
/■BANBURY 



• •••• 



1'JU. 10.— UOVKHAUK OK TI1K I.T.A. MIDLAND XltANSMlTTKH (LBKHBU1 >. 

2 niV madtan oentoar : A mV median ooot r, 

.... 1 in V mi'ilian fuiilJiur. 

West of England Region, SI-. Hilary; Central Southern Region, 
* 'hillerton Down, Isle of Wight; North East England, Burnhopo ; 
East Angliu, Kendlesfaain; Northern Ireland, Black Mountain j 

S.K. England, Dover; K.W. England, Devon and Cornwall; 
X.E. Scotland, Aberdeen; So I way (Carlisle area) Hilll(i|) Knrin. 
Estimated coverage maps for t.T.A. stations are shown in 
Eigs. 7-10. 

Future Developments 

In May, I960 the Technical Advisory Committee recommended 
to the P'.M.G. that should Bunds IV and V bo used for additional 
programmes, the Opportunity should be taken to introduce (>J.V 
iine standards, basically similar lo I hose uf C.C.T.R. (page 14) but 
with full S Me s channels (possibly divided a-a Alc/s full video 
sideband, I-L'a Me s vestigial video sideband and with sound 

carrier t> Me/a from vision carrier). Such standards would, in 
Hiesu ei re u instances, eventually be used also on Hands I and III. 
An early colour service was not recommended. Bands I and 1 1 1 
could accommodate three 40"»-line programmes (o Me/s channels) 
with national coverage or two Bl'aduie prograi nines (8 Mc/a 
channels). 



BASIC CIRCUITRY 



27 



[SECTION 3] 
BASIC CIRCUITRY 

A television receiver comprises essentially: (a) a menus of 
receiving the picture information and using this to modulate the 
beam of a cathode-ray tube (often referred to as the picture tube) : 
(b) the local lime-base oscillators atul associated amplifiers to 
provide saw-tooth signals for deflecting the beam of the picture 
tube so lha( if traces out the roster, together with arrangements 
for keeping those oscillators accurately in step with those used 
in (he original scanning of Ihe picture; (<■■ n st m. i in I -f-1 m 1 iticl 
receiver ; and (d) the necessary power supplies, including a source 
of extra high tension (E.H.T.) required for the linal anode of the 
picture tube. In practice, it is possible to use some stages for. 
more than nun of these ('unci ions, and Ibis helps to keep down tho 
total number of valves required. 

Although there has been some trend Inwards standard [sat inn 
of the major features of design in modern receivers, there is still 
considerable variation in circuit, details. It should be appre- 
ciated that the arrangements used are by no means the only 
possible ones, but have evolved primarily as a result of the eco- 
nomic competition to provide low-cost but relatively dependable 
receivers capable of providing a medium-sized picture bright 
enough for daylight viewing. In some respects notably in the 
quality of the sound — few current receivers do justice to the 
standards of transmission. 

Typical Receiver 

Fig, 1 shows tht! block outline of a typical modern receiver. 
It will be seen that the main sections are as follows ; 

(1) A Tuner Unit. This Bret amplifies the incoming vision 
and sound signals on Hand I or Hand ill and then converts them, 
usually to intermediate frequencies of 34*ria Mc/a vigjum and 
38-li) Mc/s sound. The timer is generally built as a soparate 
sub-unit and comprises mi U.K. cascode amplifier using a 
doiible-triode valve such as the PCC84, 30L1, etc., or the higher- 
slope types PCC89, 30LI5, etc., the gain of the li.F. amplifier 
being governed by an A.G.C. line. The frequency changer stage 
is almost always a triode-pontode (3001, PCF80, etc.) with the 
pentode see t ion used as a mixer and the triodc as tho local oscillator. 

(2) A Vision Receiver. The output from the tuner unit is 
normally fed to two stages of I.F. amplification (sometimes three 
stages are used for fringe-area reception). These stages have to 
handle the full baud width of the vision signal, and (his limits the 
possible gain per stage. The first l.F. stage often forms part of 

2fi 



the sound channel, and is generally connected to the A.G.C. line. 
The second I.F. amplifier opurntes at a fixed gain. Typical 
valves in these stages are: EF85, EF80, 30F5, 6F19, 6F23, 
6BW7, Z329, otc. The output from the final I.F. stage is fed 
to a video detector, which may bo either a valve (EB01, 6D2, 
etc.) op a germanium diode (OA71, GEX35, etc.), High- 




aw 



amplitude peaks of ignition or other interference are then usually 
removed from the signal by means of interference limiter circuits, 
and the video -frequency signals together with the synchronisation 
-igimls are amplified by a video-amplifier, which is usually a 
single valve, such as the EF80, 30F5, etc. 

(3) A Soma! -Chun net. Receiver. Since the sound transmissions 
arc always spaced exactly 3~> Mc/s away from the vision carrier, 



28 



TELEVISION ENGINEERS' POCKET BOOK 



it is possible for these to be amplified and converted in the same 
toner unit as the vision signals. As stated above, it is also 
common practice for the sound signals to be further amplified 
together with vision signals in a common I.F. stage, although 
some makers prefer to separate the sound and vision signals 
immediately after the tuner unit. There is, however, always at 
least one I.F. stage used solely for the sound channel. This final 
I.F. stage is followed by a diode detector {valve or crystal), and 
the signal then passes through interference-limiting circuits. In 
some receivers the A.F. signal then goes immediately to a power- 
amplifying stage; in others a triodo-pcntode {PCL82, 30PLJ, 
etc.) is used as a two stage A.F. amplifier. 

(4) Frame and Line Time-bases. The time -bases are required 
to provide 50 c/s (frame) and 10,125 c/s (line) saw-tooth scanning 
signals in order to deflect the electron beam of the picture tube 
both vertically (frame) and horizontally (line) and so trace out 
the raster. These scanning signals are prochiced independently 
by frame and line generators, subsequently amplified and fed to 
deflector coils mounted around the nock of the picture. To 
control accurately the generator frequencies, synchronising 
signals are derivod from the incoming vision signals by means 
of a synchronising separator stage, passed through further net- 
works to distinguish between the line and frame syne, pulses (see 
Section 1), and then used either to trigger directly the generators 
or — in the case of line " flywheel " systems — to control indirectly 
a free -running line generator. 

(5) E.H.T. Supply. All modern direct- vie wing receivers de- 
rive their source of E.H.T. from the high voltages which are 
produced across the primary winding of the line output trans- 
former by virtue of the rapidly changing current during the 
return of the scan stroke to the beginning of the new line (the 
" line-flyback " period). The peak pulse voltages produced at 
t In- anode of the valve are of the order of a few kilovolts and would 
be too low to be used directly, they are therefore stepped up by 
means of an overwinding on the primary of the line output 
transformer. These E.H.T. pulses are then rectified. To 
provide the damping needed to reduce " ringing " and also to 
improve the efficiency of the system, an "efficiency diode " is 
incorporated. As this diode provides a boost voltage which is 
added to the H.T. for the lino output valve (and can be used for 
other stages) it is sometimes referred to as a boost diode. 

((i) Control Circuits, Some receivers, particularly those in- 
tended for fringe-area reception, incorporate fairly elaborate 
control circuits for the provision of automatic picture control 
and flywheel synchronisation. 

The circuits used in those various sections will now be con- 
sidered in more detad. 

R.F. Stages 

A stage of R.F. amplification is invariably incorporated in a 
(1) to improve the signal-to-noise ratio by 



BASIC CIRCUITRY 
-o H.T.+ 




29 



OUTPUT 



Flu. 2 (a).— Pentode R.F. Amplifieh Stack Fic 2 (£>).— IUsicCascodkAm™- 
f(»k Uaud l Receiver. fieis. 

amplifying the signal before frequency conversion (the amplified 
signal will swamp the " noise " contributed by the mixer, which 
inherently contributes more noise than a straight amplifier) ; 
(2) to reduce the possibility of second channel interference and 



Pi 0. 8.- Tuhrm 
TtfHEB Unit Km 

JIAXD I/BASD 111. 

TUo unit provides 
Miitiutt on 34'6,"i Mc/s 
(vision) and ;»8-lu Mcfe 
frminii). VI (SOLI) is 
a oasoode li.F. ampli- 
nVr: V2 (.11)01) is ;i fcri- 
'iilt'-pentodfi frequency 
chnnger, vib 



television receiver 




30 



TELEVISION ENGINEERS' POCKET BOOK 



other forms of spurious response ; (3) to isolate the oscillator from 
the aerial and so minimise radiation which could interfere with 
other receivers or services. 

Conventional pentode R.F. amplifiers of the type shown in 
Fig. 2 (a) were widely used before the advent of Band III, LI 
and L2 are tuned by a slug and the stray capacitance. Rl is a 
pre-set gain control " sensitivity " to avoid overloading the 
following stage in areas of high signal strength. 

With the higher frequencies of Band III it is very difficult to 
design a conventional B.H\ amplifier that will give equal gain 
throughout the necessary tuning range. For this reason, a 
circuit known as the scries- connected eascode has been adopted 
in Rand I/III receivers. The basic form is shown in Fig. 2 (ft), 
where two triodes are seen to bo connected in series. The second 
triode may have its D,C. grid voltage fixed by means of a poten- 
tiometer and, acting as a cathode follower, holds the anode voltage 
of VI very nearly constant. The anode current of VI still flows 
in the load formed by the cathode input impedance of V2, but. 
with the anode voltage constant, the behaviour is that of a 
pentode having no screen current and no partition noise. From 
the signal point of view, V2 is a grounded -grid triode, is stable 
and produi't's gain with a good noise factor, VI produces tittle 
gain, duo to the low load, but has a high input impedance- 
allowing a good matching circuit, which helps the noise factor — 
and (loos not essentially require neutralisation. 

On the higher frequencies the noise factor is improved by 
neutralisation, and this is often incorporated; for example, by 
the bridge circuit formed by the 1-7 -pK and o-pF condensers in 
Kig- :S. Special double triode valves have been developed for 
this application, including high -slope valves, using what is known 
as ' ; frame grids T '. These have a special form of grid construc- 
tion which provides a high degree of electron control. 

Mixer and Local Oscillator 

Various frequency conversion circuits were used in Band I 

receivers : most common was the pentode mixer, either with a 
triode oscillator or in the self-oscillating mixer {see Fig. 4), but 
triode and hexode mixers were also used. In Fig. 4 the oscillator 
coil L3 is connected between the control and screen grids. The 
signal is fed to a tap on the oscillator coil, which is at zero- 
oscillator potential. L4 is the anode load tuned to intermediate 
frequoncy, and in the particular circuit shown R2 acts as a damp- 
ing resistor to secure adequate band-width, since the input 
damping of the next stage is not so great as at the higher signal 
frequency. The " intermediate frequency " output includes 
both the picture and sound information, and is thus really a band 
of frequencies some 4 Mc's wide. 

Since the introduction of Band I/III tuners, a triode-pentode 
valve with internal screening between the sections has been 
almost invariably used. The triode oscillator output is lightly 
run pled to the grid circuit of the pentode mixer. The oscillator in 



BASIC CIRCUITRY 







Fio. 4. — Frequency 

OllANUEH USIXCJ A SliLy- 

oscnjiATrsa R.t'. Pen- 
tode. 



most turret tuners functions by means of a feedback coil, but the 
Hartley circuit, is often used in incremental switch tuners (see 
" Channel Selection "). The main problem associated with the 
oscillator stage is that of obtaining sufficient stability to avoid 
the need to readjust the fine timing control except when changing 
from one channel to another {in some designs the fine tuning 
control has been eliminated). This requires that the oscillator 
drift should not exceed about ±100 ke/s. Stability is achieved 
partly by having a relatively large capacitance across the oscil- 
lator tuning circuit, which thus swamps the changes in valve 
capacitances causod by a change in temperature, and partly by 
the use of negative -tomporatu re coefficient capacitors, chosen to 
compensate for the temperature coefficients of the other com- 
ponents, 

ilost modern receivers have intermediate frequencies on, or 
close to, the B.R.K.M.A. recommended frequencies of 84*62 
Me/s vision and 3S- lf> Me's sound. These figures were chosen in 
provide maximum freedom from interference from harmonics of 
local stations, direct breakthrough, second channel, etc. For- 
merly much lower intermediate frequencies were popular (see 
• s ect ion 13) on account of the higher gain per stage. 

Channel Selection 

The advent of Band III transmission brought about the 
necessity of manual channel selection by the set owner. Some 
early Band I/III timers used a simple switch system for selecting 
bet ween three sets of aerial, R.F. and oscillator coils. The most 
common system in current use, however, is the turret tuner, 
which provides for fitt ing t welve sets of aerial, R.F. and oscillator 
'"oils on a rotating drum so that the appropriate set of coils for 
the channel required can easily be rotated into circuit. Alterna- 
tive systems also currently used are incremental switch and 
per j [inability tuners. In the incremental switch type successive 
additional inductances {small coils of a few turns) in the aerial, 
R.F. and oscillator circuits arc brought into circuit by means 
"' a rotary wafer switch. In the permeability type the aerial. 



32 TELEVISION ENGINEERS" POCKET BOOK 

I :.!•". and oscillator cores aro ganged together for common adjust- 
ment. Typim! turret and switch -tuner circuits are shown in 
the Alignment Section. 

Intermediate-frequency Stages 

The I.F. stages are required not only to provide the bulk of 
i lie gain needed to build up the aerial input signal voltage {from 
about 20 fiV upwards) so as to provide an output from the video 
detector of about 2 volts peak white but also to separate the 
vision and sound signals and to provide protection against 
adjacent channel interference. The band -width of both the 
vision and sound I.F. response must be sufficient to allow for 
oscillator drift to accommodate double-sideband sound band- 
width of about 20 kc/s and single-sideband video informal ton up 
to 3 Mc/s. Since the gain of a valve varies inversely with the 
band-width, ii i-- easier to obtain the neoessan gain on the sound 
channel than on the vision channel. In older models it was 
common to obtain the necossary vision band-width by "stagger" 
tuning tho tuner circuits, each circuit being tuned to a slightly 
different frequency. Modern circuits, however, more often use 
band-pass coupling transformers, often to quite complex design. 

Fig. 5 shows a modern vision I.F. strip dosignod for use with 
high-slope frame-grid valves capable of providing extreme fringe 
reception with only two I.F. stages. The circuit associated with 
1.2 is an adjacent -channel trap and would bo tuned to 33- 15 Mc/s. 
Both sound and vision signals jippear across the anode load L3a. 
The sound signals are then fed off to tho sound I.F. stage and 
prevented from reaching the grid of V2 by means of a bridged-T 
filter formed by L4, the two 27-pF condensers and tho S-2k 
resistor. This type of filter sharply rejects a single frequency 



SOUND AND VISION 



4- 190V 




XlOOO 



T PF 
OA70 VIDEO 

>| pfetiW'-f— - — *■ 



ppF 



RFC 



fl - oc - sound tak;: off 

Fir. ,'.. T.F. and DmSSOTOn S'iAia:s unii ■' I'immk-chiii " PBOTOWB. 






BASIC CIRCUITRY 



33 



without appreciably distorting the response- curve on nearby 
frequencies. In this circuit the stages are neutralised by means 
of the 10% common screen/anode decoupling condensers. I.F. 
stages using lowor-slopo valves are seldom neutralised. 

Considerable variation in the inter-stage coupling and in the 
soiuid- rejection traps occurs betweon different models, and some 
of these differences can be noted from a study of tho representative* 
receiver circuits provided later in this section. 

Detector and Video Amplifier 

After the I.F. stages como tho detector and video amplifier; 
Fig. 6 is typical. The diodo load R T is only 3-5 k : tho effective 
load at, say, 3*5 Mc/s will not be sensibly lower than at, say, 
25 c/s, though it is shunted by stray capacitance whose reactance 
falls with increase of frequency. Without considering any 
special compensation circuits, the response will be 3 db down at 
tlie frequency for which IttfOR = I. A load resistance of 5 k 
therefore postulates stray capacitance of only 9 pF. L B is an 
1 .F. filter, and if the stray capacitances at each ond (shown dotted} 
are considered, it approximates to a conventional low-pass filter. 
Here, too, a high I.F. simplifies filtering, as it is more remote 
from the upper video froquencios. This video stage, giving a 
negative output, drives the cathode of the cathode-ray tube. 

To improve the high-frequency response, " top-lift " circuits 
may bo incorporated in tho video amplifier : an inductance is 



VC.R.T./ 




FIG. G. — DETECTOR AND VIDEO AME-LlfJKIt, 

inuluded in the (resistive) load and choson to resonate with 
the Btray capacitance at & frequency above (e.gr., ^'2 times) 
the highest required frequency. This maintains the load 
impedance — and hence tho gain — up to a higher frequency 
than for an uncorrected circuit. The inductance is given by 
L == p.Cll*, where p has a value 0-3-0-5. 

Many receivers incorporate a cathode follower in tho video 
output stage. This became popular beeause of tho greater 
output, required when the 2 1 -in. picture tube came into common 
uso. Whilst a cathode follower stago has a voltage gain of less 



34 



TELEVISION ENGINEERS' POCKET BOOK 




VIDEO 
I2QV OUTPUT 



26pF 



Fin. 7,— Tinwi ampukiku sta«b l \c nnronvnsa k oatuoem; Koliowku. 
{Courttxij Milliard, Lid.) 

i h.ui 1, the inclusion of such a stage isolates tho first video stago 
from tho stray capacitances into which it would othorwiso have 
to work, thus enabling the gain of tin- lirst video stage to be 
increased whilst maintaining band-width. Such stages aro also 
found in 14- and 17-in. models, to effect a saving in tho number 
of I.F. tunod circuits required. Gains of up to about 22 are 
possible with a two-stage video amplifier such as that shown in 
Fig. 7, whilst a gain of about 11 was tho maximum possible in a 
single pentode stage with full bundwidt h ; recent ly however valves 

giving greater gains in a single stage have become ava ilable . 




BASIC CIRCUITRY 



35 







l-'Hi. '.I.— Vision [HXBinSBBOS SUrPUKSSION cm- 

i unp. v: conducts omasa jntkukkiiisnck 

I'KAKS. 



FIU. 8.— VtfflOH UTKKKKKKXCti Sl'lH'l SESSION ClEtCUT USING SPOT [SVKIISIOV. 



Interference Liruiters 

Interference limiters, chiefly to reduce ignition interference, 
are essential. They fall broadly into two groups, one in which 
tho gain of some valve 
is sharply reduced dur- 
ing the interference 
pulse (Fig. 9), and the 
other in which normally 
white-going interfer- 
ence is inverted to 
appear as black (Fig. 8). 

V7, a low- impedance 
diode, shunts K s , and 
is normally non -con- 
ducting with its anode 
at a potential corre- 
sponding to peak white. 
When a large-amplitude 
interference pulso ar- 
rives at V6 grid, its 
anode is driven more 
negative than for peak- 
white, and V7 cathode is carried with it, making V7 lo conduct and 
to shunt K B , thus reducing the load and gain of V6 for the duration 
of the interference. 

In the spot inverter V6 is again the video valve, and its output, 
as well as driving the cathode of the cathode-ray tube, is fed to 
the cathode of V8, a triodo whose grid is suitably biased by K lt . 
sn that at peak white V8 is just cut off. Any impulsive noise of 
greater amplitude than this lowers the cathode potential of V8 
so that it conducts, passing through C 3 an amplified signal to the 
cathode-ray tube grid, and so producing a black spot which is 
generally less noticeable than a white one. 

SOUND {.'H ANN Kb 

The general design features of the sound channel up to the 
detector stage do not differ greatly from rlie circuits used in the 
vision channel, except that the inter-valve coupling tends to be 
less complex. The tot id gain required is much t lie samo as that 
for the vision signal of tho order of 100 db (100,000: 1). The 
majority of this gain is supplied by the I.F. stages. 

The band -width of the sound channel as transmitted will be 
of the order of 30 Ice's, representing thp double sideband trans- 
mission of audio frequencies up to IS ko 8, but the receiver band- 
width requires to bo much greater than this figure would suggest. 
'I'his is partly in order to overcome the effect of oscillator drift, 
which may amount lo some 100 ke S, and partly to help in the 
-oppression of impulse interference from car ignition systems 
and electrical equipment. A broad response of the order of 
•'Oil Uc s u ;|| | M ,. :tt | that the interference pulses can be reproduced 






36 



TELEVISION ENGINEERS' POCKET BOOK 




noise 



SUP PRESS OR 



FIO. 10. — SOUND DKTliCTOE AND A.G.C 1 . OtllCUIT. 

at the detector without undue lengthening, nut I this will inako 
for more efficient interference suppression. With a broad- 
response curve it is sometimes difficult to prevent low-frequency 
vision-signal components from entering the sound channel (for 
example, the frame synchronising signals may be reproduced 
as 50 c/s hum), particularly where the user does not adjust the 
tine tuner control accurately. 

With the high sound I.F. of modern receivers— usually 38-15 
Mc/s— I.F. stage gain with conventional high-slope pentodes 
tends to he limited to about 30-41), in order to ensure stability. 
Considerably higher stage gains can be obtained with frame-grid 
valves, although it may be necessary to use some form »(' 
neutralisation to maintain stability. 

It. is common practice to control the gain of a sound I.F. stage 
by an A. <;.(*. voltage obtained from the detector stage. However, 
in somo designs no separate sound A.G.C. system is incorporated. 

The Detector 

As in the case of radio receivers, the diode detector has long 
been popular in television-receiver designs. The value of the 
load resistance will, however, be much lower Lhan in radio 
practice, and the I.F. filter will consist of chokes and very small 
condenser values (10-20 pF) in order to prevent the undesirable 
integration of interference pulses. The use of germanium crystal 
diodes has to a largo extent ousted the thermionic diode on the 
counts of low cost and low self-capacity. 

An A.G.C. potential may bo taken from the detector load, a 
suitable arrangement being shown in Fig, 10, in which a delay 
diode is incorporated. The detector circuit has, of course, to 
produce a signal sufficient to cause a current flow in R2 equal 






BASIC CIRCUITRY 



37 



to the current normally flowing from the H.T. line through E3 
and the delay diode before the delay is overcome. Delay circuits 
are by no means universal, and a compromise method is to apply 
only a part of the detector D.C. component to the A.G.C. line. 
Whichever method is used, it is necessary to reduce the impe- 
dance of the A.G.C. line to the minimum so that blocking does 
not occur in I.F. grid circuits connected to it. 

Interference Suppression 

The level at which the detector operates Li determined largely 
by the performance of the audio-output stages, which follow it, 
and also by the circuit used to provide suppression of impulsive 
interference. While audio amplifiers to provide tho required 
output (normally 1-2 W) can easily be designed to accept very 
low inputs, tho noise-suppression circuit operates best at fairly 
high levels. It is placed immediately after the detector, so that 
tho need for wide band-widths can be dispensed with after the 
interference has been reduced sufficiently, and it is not difficult 
to operate the detector to provide a demodulated output of 
5-10 V peak-to-poak (80 per cent modulation). 

One of the most successful noise -suppress! on circuits* is shown 
in Fig. 11. Resistances III and R2 are of the order of megohms, 
bo that a steady current of, say, 50 /*A flows through the diode. 
The condenser C is a critically large value chosen so that the 
time constant formed with R2 is just capable of being charged 
and discharged by the current flowing through the diodo at tho 
highest audio frequencies it is desired to reproduce. From the 
waveforms it is apparent that at audio frequencies the cathode 
of the diode follows tho anode. If, however, a negative -going 
interference pulso of very short duration appears, the diode will 
immediately cut off and the cathode circuit will commence to 
dischar ge. Before any great change has takon plane, the pulse 
ends and tho audio signal reappears at the output hearing only 
a small triangular ' : pip " instead of tho original large pulse. Tho 
further smoothing is provided to smooth out this remaining pip. 



'+) INTERFERENCE 

SUPPRESSOR 



DETECTOR 




I-'IO. II.— IM'JiilFEltKNCl'i Slil-I'KEaSIOX (JlUCUIT. 



* British Patent No. GG5,20(i. 



38 



TELEVISION ENGINEERS* POCKET BOOK 



It. is now possible to soo why so much attention has been given 
to preserving the shape of tho interference pulses and to the 
prevention of blocking. 

Audio Output 

While it can be said that any good-quality audio stage will 
suffice the needs of tho television sound channel, it is perhaps 
worth remembering that quite a lot of effort has gone into the 
production of a very high-quality signal at the output of the 
doteetor and noise-suppression circuits. Although reproduction 
may be marred in the mage areas by weak signals and continuous 
interference, and the main attention of the audience is coneeu- 
trated upon the picture, there are many occasions when the 
reproduction of the full quality will be worth while. Apart from 
this, it is probably true to say that there is no groat need for as 
high an output as is produced by a radio receiver, since the 
viewers will normally be relatively close to tho loudspeaker. 

If a noise-suppression circuit of the typo doscribod above is 
used, it must bo made in dependent of any negative feedback 
arrangement which may upset its operation. 

V.H.F.'F.M. Reception 

Many television ivmvns nuw incorporate facilities for the 
reception of Band J I V.H.F..F.M. sound broadcasting stations. 

One of tho simples* methods is to lit three additional sets of 
coils in lln 1 i iniri timer, limed In i lie local Home. Light and Third 
channels, and to arrange to switch into eirenii when required an 
F.M. discriminator, usually a ratio detector, in place of the tele- 
vision A.M. sound defector. H.T. and heater sup]. lies to the 
picture tube are switched off during F.M. reception to extend its 
life. Similarlv, the lime-ba-es mid sometimes the video strip 
nun be tnken'out of sorvico. A typical arrangement for a ootn> 
hiiied A.M. F.M. detector stage is shown in Fig. 12. VIA arts 
;is n conventional sound demodulator when the set is switched 




l'li;. 12. DBTfiCTOH sruiK OP a Hl-ier.iVKH with 
!■ vn.mi:* nut V.1U-..K.M. R» i.i-tiox. 



BASIC CIRCUITRY 



39 



to " TV 7 ", and VI B is then out of circuit. On " F.M." VIA and 
\i form a ratio detector with amplitude changes stabiliser! by 
i he \'l-/iF elect -roi\ tie condenser, and maximum A.M. rejection 







i* obtained by adjusting the balancing trimmer TCI. Dl is 
interference umiter diode on " TV "', but is switched out 
circuit during F.M. reception, 



an 

of 



40 



TELEVISION ENGINEERS' POCKET BOOK 




RATIO DETECTOR 




•:■' 



WW- 



1 



I' HI. 14-— Um Of V 1'OJNT OOHTAOT OB JrxfTliiX GERMANIUM DlOI»K Hi 

PKOVILiK .\l 'loMVI'li; PBSQtnSNCS I'ONTJtol. OS F.M. 

Ttiisls baaed on cfcaogQB oJ capacitance ol the diode wii.li ciuioges of reverse voltage 
applied across it. 

However, it is dilUcult with such arrangements to ensure the 

high order of A.M. rejection needed to overcome the "tissue- 
paper " distortion caused by multi-path (" ghost '*) interference 
in some localities. This is mainly due to lack of gain, arising 
from the high I.K. (usually 38-15 Mc/r). Adjacent-channel 
selectivity may also In 1 deficient. 

In some models an extra I.F. stage is switched into operation 
on F.M., while others use an intermediate frequency of 
10-7 Mu/a on F.M. by means of dual-channel I.F. strips, similar 
in principle to those used on combined A.M. /F.M. sound receivers. 
Another system is to use dual -conversion with a second I.F. 
of" the order of (> Mc's. In a number of models a completely 
separate F.M. unit, up to and including the ratio detector, is 
fitted. 

t/ig. 13 shows a. representative sound channel using dual 
channel I.F. stages. The anode circuit of the mixer contains 
circuits tuned to 10*7 Me s and 38-15 Mc/s, and both channels 
are amplified by V9 and VIO. The 10-7-Mc/s circuits offer 
negligible impedance at 3N-1.") Mr s, and vice versa. D3 is a 
conventional sound detector, while Vll is a ratio detector for 
the P.M. signals. The pro-set resistor P9 is adjusted to provide 
minimum output of A.M. signals. The two-stage A.F. amplifier 
{VI7A, B) is common to both channels. On K.M. reception the 
heater supplies to the picture tube and the time-base valves are 
switched off. 






BASIC CIRCUITRY 
TIME BASE CIRCUITS 



4J 



50-e s frame and I0-125-kc/s line time- bases are needed to 
produce the cathode-ray tube raster. .Most time-base circuits 



-o H.T. + 






SWITCH 




SWITCH SWITCH 

CLOSES OPENS 



Mr,. 13.— basic principle of tuk saw-tooth Gkxkhator. 

involve the slow charge and rapid discharge of a condenser. 
In some cases this is reversed. Fig. 15 shows a condenser charged 
through a resistor with a discharge " switch " dovico across 
C 4 , The switch can bo 
a gas-dischargo valve 
(thyratrou), but the 
blocking oscillator is 
more usual. It oper- 
ates as follows (Fig. 
16) : tho valve is con- 
ducting, any small 
variation at, the grid 
will be amplified and 
fed back to tho grid. 
The result is cumula- 
tive, and violent oscilla- 
tion results. On the 
positive half-cycles 
grid current flows, pro- 
ducing such a large 
negative bias across C s that the valve is cut off. The negative 
charge on Cj leaks through R, s until conduction again takes placo. 
The build-up ia rapid, and the valve continues to oscillate for a 
short period and is out off for a longer period. During oscillation 
the valve draws a current, mostly from 4 , which charges through 
H, s during the period of cut-off. The oscillation frequency of the 
valve is incidental : the fact that it discharges C 4 is important, as 
also is the interruption frequency, which is controlled mainly by 
the (adjustable) time constant C S R, 3 . Tho latter is the " hold " 
control. Positive-going synchronising pulses, fed to the grid, 
kick off the oscillation at the right instant to keep the received 
picture in stop with that transmitted. 




Fill. 



6 SYNCH 



16.— TUftt-BASS GEHKRAIOB USING A 
BbOGKDra Oscillator. 



42 



TELEVISION ENGINEERS' POCKET BOOK 





Fhi. 17.— Basic Min.Ti-vmit.vion Omcrars. (a) asouk-to- 
onm Covplku, (ft) Cathode OOUFUBD. 

An alternative, popular time-base oscillator is the multi- 
vibrator, of which there aro two basic varieties, tho anode-to- 
grid (sec Fig. 17 {a)) and the cathode coupled (son Fig. 17 (ft)) 
versions. 

Tho action of the anode-to-grid coupled multi-vibrator is as 
follows: Assume that, at the start, VI is cut-off, V2 is passing 
current and C2 is charged. The anode voltage across R4 falls 
until it reaches a- point where 02 discharges through R2, so driving 
the grid of VI sufficiently positive for V I to conduct. When this 
happens, the voltage across III doereases. Tho voltage on the 
grid of V2 also decreases, until Y2 is cut-off. Tho position is 
then reversed, CI discharging through R3 and the grid of V2 
becoming positive so that V2 again passes i-urivnt. This process 
continues. Whilst V2 is cut-oiT, C.„,t charges through R4; when 
Y2 is conducting, however, C„ ut discharges, so that a saw-tooth 
waveform is produced. As shown, the syne, input is fod to the 
mikkIp .>t' \'i. Ii is also possible, however, to arrange few the 
sync, input to bo fed to the grid of VI . Control over the oscillator 
speed is offected by making R3 variable. 

Tho cathode-coupled multi-vibrator circuit operates in the 
following manner: Assume that-, at the start, V2 is cut-off, VI is 
conducting and CI charging through R2. In this condition. Cut 
will bo charging through R5, and the negative charge on the grid 
of \ '2 will he leaking away through K4. When the grid of V2 is 
sufficiently positive, the valve will begin in conduct and there 
will be a drop in the voltago aeross the common-cathode resistor 
R3. This voltage drop will lead to a rise in voltage across H2, 
with a corresponding drop in the current. Whilst V2 is in this 
way cut-off. CI discharges, driving the grid of V2 more positive 
so that V2 is conducting sufficiently for C„ u t to discharge. As 
the positive charge on tho grid of VI leaks away through Rl . Vi 
will again start to conduct', CI will charge through R2, and the 
voltago drop across R3 will again lead to V2 being cut-off whilst 
C m ,t charges through Re. Control over the hold is effected by 
making R4 variable. The circuit is easily triggered by feeding 
the sync, pulso to tho grid of VI. In practice, a number of 



BASIC CIRCUITRY 



43 



Fi«. is.— ACoaaos Yaim wr 

OF THK Mtn.TT-rmRATOR 
TO A LIKE TUffl-BASS. 

Tbe teed bark to Tl is vin 
the 47jiF condenser couuected 
u> a tapping on tbe line oatpat 
transformer. 




trariaxtte of these basic circuits aro often to bo found. In a 
number of sets, the screen -cathode section of the output valve 
Conns one section of tho multi-vibrator. A more common 
arrangement, in which the line output stage forms, in effect, part 
of a multi- vibrator circuit is shown in Fig. 1 8. In several current 
models a combination of these two systems is used in the line 
time-base, the screen -cathode section of the output valve forming 
one section of the multi-vibrator during tho warming up period 
before the efficiency diode is brought into action, the mode of 
operation then changing, the main feedback being via a condenser 
connected to a tapping on tho line output transformer. If tho 
anode resistor of one half of a multi-vibrator is connected in the 
neroen circuit, this enables tho output to be taken from the anode 
circuit, and, since tho output load is then coupled to tho oscillator 
only via tho electron stream of the valve, variations in tho output 
load will have much less effect on the frequency of oscillation. 
This arrangement is also used in a number of models. 

In line output stages it has also been common to use the screen 
and grid of the output valve in a blocking oscillator arrangement. 
A separate transformer, or a section of or overwinding on the 
line output transformer, may be used. 

The saw-tooth voltage is transformed to a saw-tooth current 
for the deflection coils by feeding them from a pentode whose 
high anode-slope resistance swamps the deflector-coil inductance. 
The frame output may bo fed directly, but the line coils are 
always transformer-coupled, as the deflection is larger and the 
available time shorter. The E.M.F. induced across the coils 
also leads to insulation difficulties, so a step-down transformer 
of ratio between 4 and 12 to 1 is used to feed them at low voltage 
and high current (up to 1 A peak). Largo voltages still appear 
at the primary, and tho line -output valve has to withstand them 
without flashovcr. 



44 



TELEVISION ENGINEERS' POCKET BOOK 




*-H.T,-»- 



FlO. 10. -Effect of " RlNU- 
1MJ " ON TiMB-TJASE 
WAVKFOHM. 



A difficulty is " ringing " (aclf-oscillation) between the in- 
ductance and stray capacitance of the circuit, resulting in the 
waveform shown in Fig. 1!). A shunt resistor will damp the 
oscillations, but aa it is also present during the forward stroke, the 
efficiency of the circuit is reduced. A typical circuit is shown 

FlO. •>».— LETT! TIME-BASE 

Output Stage siiowisu 
toe efficiency diode 
vii. 

in Fig. 20. VI is the 
line-output valve, and 
VI 1 is the damping or 
" efficiency " diode. 
It absorbs no power on 
the forward stroke, but 
provides a voltage of 
about 150 V across C e , 
which is added to the 
H.T. for VI and for 
the first anode of the 
cathode -ray tube (and 
often also for the frame 
time-base output). 

The waveform pro- 
duced is not a linear 
saw-tooth, since the voltago appearing across a condenser charged 
through a resistor is exponential. If the condenser is charged 
through a pentode, a constant current flows and linearity 
results. 

It is now common practice to operate the line output pentode 
" below the knee " of t lie /„/ V a characteristic, in which condition 
the grid potential has little effect upon anode current. The main 
advantages of this mode of operation are that the E.H.T. regula- 
tion is improved, and the fall off in scan power during the life 
of the mil |. ui valvo is reduced. For example, a drop of 25 per 
cent in the peak anode current of the valve need result in a loss 
of scan power el' only about 0-25 per cent. This greater con- 
sistency of .ml put has made it- possible to dispense with the 
conventional forms of width control. 

Tuned Leakage Inductance Transformers 

If the leakage inductance between the primary and the E.H.T. 
overwind of a line transformer is made to resonate with the 
effective capacitance across it, to a frequency about 2-7 times 
that of the effective primary inductance tmd capacitance, then 




BASIC CIRCUITRY 



45 



the peak voltages on the anode of the line output valve and 
cathode of the boost diode valve are reduced by about 20 per 
cent, while the voltage on the E.H.T. rectifier anode is increased. 
Also, with this 2-7 ratio, the ringing voltage of the leakage in- 
duct a nc is /.i •!■. i ai I lie end of the flyback period and does not 
coot inue during t he scan. This moans that there are no striatums 
on the raster due to leakage inductance between tho primary and 
E.H.T. overwind. This system is commonly used for wide-angle 
tubes. 

De-saturated Transformers 

Since about 1 955, some line output trasn formers have had 
de-saturated cores, which is to say that the magnetising (lux 
arising from the direct current (lowing in the windings is can- 
celled out. The transformer winding is split at the cathode- tap 
of the efficiency diode and a coupling capacitor inserted. It will 
bo seen from Fig. 21 (a) that the anode current for the line output 
valve passes through both sections of the transformer but in an 
opposite sense, so that the D.C. component is largely neutralised. 
In this arrangement the H.T, feed is through a largo choko which 
may bo marie variable to form a width control. The system 
provides greater efficiency for a given core section and is also 
useful in reducing the 10-ke/s lino whistle. 

A modification of this system has now been introduced in 
which the feed choke is not required, being replaced by the line- 
deflection coils and the associated shoi ■led-turn sleeve. In 
practice, component values may differ from those shown in 
Fig. 21 (b), derived from a Milliard design. 



DEFLECTION COILS 





i'"n;. H. D&SAX1 jivri:n line-oitht tu.\ssfiirmi-:i:s. 

(")TIip haste oystcHti. (ft) A modified system with toned leakage Inductance urn) 
linearity sleeve. ' 



46 



TELEVISION ENGINEERS' POCKET BOOK 



Shorfced-turn Linearity and Width Controls 

Owing to the varying impedance of components in the line 
time-base during the scanning cycle, an uncorrected time-base 
would cause Hie picture In he stretched on I he left ant) crumped 
on tin; right. The usual remedy is to conned a saturated reactor 
in series with the line-scanning coils; this can he arranged (o 
compensate for the impedance variations so that a relatively 
undistorted picture is ohtained. Linearity controls of this type 
are found on many modern receivers. A disadvantage of this 
system, however, arises from the tendency of the reactor to 
induce " ringing '*, which appears as vertical striatums on the 
left-hand side of the raster, and it also consumes some of the scan 
power. Kinging can be reducod by damping the saturated 
reactor by means of paralleled resistors, but this reduces the 
efficiency of the control and increases cost. 



ONE SCANNING COIL 




I'm. 38 ilifn. l.ts i:\n- 
rrv BMocvx i\ Position 

\i;oi sn \>.ch Of I'tc- 

rura rem 



J -" i ■ : . *j:'. (Mote).- V.uuims 
Porhs Taken itv Pleeve 

SHOWING I 'hi I. I.ihiI'S 1N- 

sroa NoN-ooKoronvn 

POftUBS. 



Now widely used is a linearity control which does not introduce 
ringing. It consists basically of two rectangular loops of mctnl 
foQ lixed to a cylindrical fori nor and placed around the neck of 
the picture tube beneath the line-scan coils. There is no direct 
electrical connection between the loops and the scanning coils, 
but a current is induced in the loops by the magnetic held, and 
this in turn affects the current in the scanning coils. By adjust- 
ment, of the physical push ion of t he loops the linearity of the line 
time-base. may be controlled. There are severs I possible versions 
of ibis form of linearity control, see Kig, 23. 






BASIC CIRCUITRY 



47 



The adjustment of the loops is critical, and may be made more 
difficult by the effect of other assemblies on the neck of the tube. 
For this reason the sleeve carrying the linearity control loops 
may be cemented to the scanning-coil assembly, and in such 
eases it is advisable not to disturb the adjustment when changing 
l ubes. 

In recent modols this sleeve technique has been extended to 
act as both linearity and width control. This is possible because 
modern line output stages are designed to provide a nearly 
constant output throughout the life of the valve. By dispensing 
with the pre-set width control it is possible to conserve scan 
power. 

Where the shorted-turn sloeve is used for width and linearity 
adjustments, the usual method of setting, using Test Card C, is 
as follows: 

I'intitre shape. Adjust the sleeve to provide symmetry of the 
horizontal and vertical lines and corners by rotating the sleeve 
about the neck. This adjustment is for minimum coupling to 
the frame coils which would cause poor interlace and geometric 
distortion. 

Width and Linearity. Slide the sleeve alonff the, neck without 
rotating it until the correct width is obtained. With 110° tube 
masks this may require some horizontal overscan. Correct width 
sitting should also provide good linearity. It should be noted 
that a sleeve inserted too i\\v info the defied -ion-coil assembly 
may cause overheating of the deflection coiis. 

On tubes having an ion trap, the ion-trap magnet should he 
checked after any adjustment of the sleeve. 

Width control by means of a tapped line output transformer 
is also now common, as this method also eliminates the saturable 
reactor type of control. 

Synchronising-signal Separation 

While tho whole television signal is fed through the early 
stages of the receiver, the synchronising signals must be removed 
to be fed to the time-base circuits, either before or (normally) 
after the detector stage. In the British system the synchronising 
pulses occupy 0-30 per cent modulation and the picture 3(1-1 lit) 
per cent, BO that an amplitude filter can he used. This may con- 
sist of a diode biased to the amplitude of the synchronising 
pulses so that it will conduct only when the picture is present. 
I he output will therefore consist only of the synchronising 
pulses. 

Alternatively, a peutodo may be used with an anode voltage 
of about. 10 V und screen of about 50 V, Fig. 24, which gives 
the characteristic shown in Fig. 25. Current models for many 
years have used pentode synchronising-pulse separators because 
of the amplification possible. 

The line synchronising pulses must also be separated from the 
frame pulses, and, as they arc of the same amplitude, a time or 



48 



TELEVISION ENGINEERS' POCKET BOOK 



TO V f 

4 



-4 



SYNCH 
PULSES 



■o H.T.+ 



1 

T-ww- 



V|3._ 

i — mjw £I_, 



;r 7 



ill 



BIAS=SYNCH PULSE 
AMPLITUDF 



Fid. 2 i. — SVN< II IK >N ISINJi Sk.I'AUATOR T78INO SATURATED V.M.VC. 



length filter must be used. A usual method is to apply the- pulses 
to two filters, known as differentiating and integrating circuits. 

In Fig. 20 the time 
'a constant ln , R ls is 

short compared with 
the length of the line- 
synchro nisi rig pulses 
■. (about 2-5 oS, e.g., 
C l0 = 50 pF and 
R 16 = 50 k). The out- 
put voltage (across 
R u ) rises sharply to 
approximately the full 
value, but, as Ci 
charges rapidly, the 
voltage across R , s falls 
to give the waveform 
(Fig. 20) the time eon- 




I [L 



PIG, 85.- Oi'i:itATiN(i 

I MM 1 ITII IN.-! uK VI 3. 



shown. For the integrating circuit 

stant is long compared with a line-synchronising period (about 
50 /iS) and, consequently, the voltage appearing across C tl is 
small for lino pulses, hut when the eight broad 40-ftS frame 
pulses arrive, the voltage across C u builds up. The two states 
(at the end of even and odd frames) are shown. This appears 
to produce a fiat -fronted pulse, but when the scale is considered, 
the eight broad pulses total about 400 pS and the rest of the 
frame period 19.000 fxS, a ratio of nearly I : 50, so that the pulse 
may be steep enough to ensure good interlace. Kurt her shaping. 
however, may be applied. 

To reduce the effect of residual lino pulses on frame synchroni- 
sation, a series-connected clipper diode is frequently incorporated 
in the frame -synchronising circuit. This gives a short charging 
and slow discharging time constant to the frame-synchronising 
separation circuit. Alternatively, a diode to earth may bo 
added and biased so as to conduct during the line pulse period, 



ih 



c lO 

| R I5 OUTPUT 



V IN 



(a) 



BASIC CIRC 

— o 



ji n fi 



o vww- 
INPUT 





m 



49 



— o 



Cu OUTPUT 





vinji n nnnnr 



° uT -y-y~V 



VOUT. 



It.;. 88, -WAVEFORMS PRODUCE!! BY: 
(a) 1UFFKKKNT1ATING CIRCUIT, ASH 

(6) rsTMiRATrsf; cincrrr. 



viN_n n__n_rinnnj 



V OUT. 



i hereby removing residual line pulses from the train of pulses fed 
to tho frame generator. 

Interference to the picture (faint white lines, slightly tiltod, 
across the picture) is sometimes caused by the frame flyback, 
and suppression, in the form of a voltage applied to one of the 
picture-tube electrodes, is often incorporated to cut off tho 
scanning beam during the frame flyback period. 

Power Supplies 

The H.T. is derived by half-wave rectification from the 
mains, and so is limited to about 180 V. Hpecial valves have 
been developed to operate with this rather low H.T. voltage, 
I 'in (he line and frame time-base outputs and the cathode-ray 
juhe lii si anode operate more satisfactorily OTJ ftboul 300 V. 
The extra voltage can bo derived from the line time-base output 
as described above (under " Time-base circuits "), and is known as 
the " boost " voltage. 

An increase in the efficiency of t he H.T. rectification, and hence 
a somewhat higher H.T. line, is possible by the use of silicon 
rectifiers. The voltage drop across these rectifiers is much 
smaller than that across metal (selenium) or valve rectifiers, and 
'Iocs not increase with age. 

The E.H.T. may be derived by at least three methods : (i) from 
tbe line flyback; (2) by rectifying tho output from a separate 
oscillator operating at about 40 ke/s; and (3) by tho ; * ringing 
MKA» m method. In (I), see Fig. 27, VI0 is the line-output valve, 
V 11 the efficiency or boost diode, already dealt with, VI 4 is the 
high -voltage rectifier, whoso heater is fed from an auxiliarv 



so 



TELEVISION ENGINEERS' POCKET BOOK 



t i 

1 



-o H.T.+ 



;c 6 




TO DEFLECTION 
~ COILS • 

! \. v is 



-A 
~B 
--B 



~--r -O 



-^*^ 



... 

T 



i" V 



*-*\ 



V| 4 



E.H.T. 



FM. '27.— USB FLTIMCK E.li.T. CIKCU1T. 

winding on tho transformer, and C ia tho reservoir condenser 
(500-1000 pF). The dotted connections and components show a 
voltage-doubling circuit though these are seldom used. 

Id practice, nl I modern direct -viewing receivers use i he 
line llvhaek method nl" K.H.T. generation, developing voltages 
up to about III kV without voltage doubling h\ intunis of an 
E.H.T. overwind on the lino output transformer. Some models 
incorporate E.H.T. regulation using either b nonlinear resistive 

element., such as the " Metrosil ", which nets us mi " overflow " 

to prevent the voltage rising above e Specified \alue ! ;ins of 

adjusting i his component is sometimes provided), or alterna- 
tively, may hsp one of the more elaborate feedback control 
systems, in wliieh n small proportion of* the output is rectified 
and used to control the bias on the output stage. 

Because of the high frequency nf line flyback K.H.T. systems, 
only n small value smoothing condenser is required: this is 

usually obtained by 
coating part <>\" the 
inner nntl outer surface 
of the picture tube 
with a conductive 
material (A qua dag). 

D.C. Restoration 

Tho picture signal as 
i ransmitted is a D.C. 
signal in that all its 
variations start from a 
daf urn and an- on one 
sido of it, see Fig. 2"! («■). 
When such a fluctuat- 
ing D.C. signal is applied to interstage couplings (e.g., in tho video 
amplifier), only the A.C. part can be passed on, with equal areas 




1'iu. «L— D.O. Krs'iaii.vriON. 



BASIC CIRCUITRY 



51 



NORMAL T" 
EXCUR5ION 
OF CRT. i 
GRID - 1 - 

(OR CATHODE) 



t 




l-li I. J'.i («). T'K.TLKl-; SIGNAL AS 
THANsMITl'Kn, 



Z\T. 

















t 

C RT 


i «:. as 9), Bftwsto* urn* 

STACK COITI-TNIS. 


1 


wm 






'IT 


•-i r GRID 
u EXCURSION 

1 



of excursion on each sido of a datum, Fig. 29 (b). This means, 
as shown, that for driving the cathode-ray tube a much greater 
total swing must be accommodated. To improve matters tin- 
D.C. condition can be restored a.s shown in Fig. 28, in which the 
diode will conduct, as soon a« the point A goes positive, thus 
ensuring that- no part of the signal appears above the datum. 
The polarity here dealt with is negative in accordance with the 
output from V<» above. In modern sets, either direct coupling is 
used or alternatively the D.C. is not fully restored. 

AUTOMATIC PICTURE CONTROL 

All but a very few Band I/III receivers incorporate some form 
of vision automatic gain control (A.P.C.). The different Rand 
1 and Hand 111 signal strengths likely to bo encountered make 
Hiis feature desirable if changing from a Hand 1 channel to a 
Hand III channel is to be made free of considerable readjustment 
of t he sensitivity and eont rast conl rols. An nlternat ive approach 
in this problem! ^^ <n several models, is the use of independent, 
pre-sef. sensitivity (li.F. gain) controls for each Band, 

Mean Level A.G.C. 

The simplest, and one of the most common, forms of A.l'.r. 
is to sample tho waveform appearing in the grid circuit of the 



1 ■!■:■ :■'».— Mean Lkvki, >..;., . 
&rantsi Bampukq shi.vai. at 

GRID ok 8YBC SKl'AUATou. 
I'l IS A DELAY laonK. 




A.G.C. DIA5 



52 



TELEVISION ENGINEERS' POCKET BOOK 






Synchronising separator stage. This signal is D.C. restored by the 
grid current of the synchronising separators. The control volt- 
age derived from this source is then fed back, as bias, to the 
R.F, and, sometimes, one or more of the I.F. stages. The con- 
trast rout ml then lakes i ho form of a [Kit cut iometer determining 
the level at which the A.G.C. begins to operate. With such a 
system, it is common, as shown in Fig. 30, to Include a chimp 
diode to delay the effect nf the control voltage s< > thtil. the gain 
i>f Mil' receiver strip is not reduced below (-be r< ■< nun 1 1 ainplilira- 
tion level and to prevent the A.G.C. line going positive when 
the contrast control is operated. It is also common to include 
a diode to provide additional delay to the voltage applied to the 
K.K. amplifier stage, in order to retain maximum R.K. amplifica- 
tion and thereby obtain the best noise factor. The suppressor 
grid of a suitable valve. «.j/., synchronising separator or l.F. 
amplifier, is often used as a delay diode. 

Gated A.G.C. 

The system so far mentioned is based on the moan signal level. 
A disadvantage of this system is that the A.G.C. vol (ago varies 
with changes in the picture content as well as with changes in 
the signal strength. Since, however, it is comparatively rare 
for the picture content to vary widely— i.e.,, as would happen 
if an all-black picture followed immediately after an all-white 
one this disadvantage is not so great as it might appear. 
Further disadvantages are the low gain and long time constant 
(necessary to prevent re-modulation of the sound or vision) of 
the circuit. The long time constant means that the circuit- will 
not respond to quick, small variations in signal strength such as 
those caused by passing aircraft. 

To overcome the disadvantage of changes with picturo con- 
tent, especially in receivers intended for fringe-area recept ion, 
where considerable picture fading may be experienced, a " gated " 
system is oflcn used. A number of different arrangements have 
been employed. In gated systems the amplitude of the signal 
is measured at some time during the picture waveform when it 
i* at a known level, the receiver gain then being controlled 
accordingly. In the British television system the black level 
(representing 3(1 per cent modulation) is kept constant at the 
transmitter and is radiated for a few micro-seconds following 
tin- line synchronising pulse and for a few lines following Ibe 
frame pulses. By basing the control bias voltage on these 
periods, the receiver gain, with A.G.C. applied, can be kept 
independent of the picture content. 

It is more common to sample the signal during the "back 
porch " period following the line-synchronising pulses than to 
sample the strength of the carrier at tho frame frequency, and 
an arrangement for sampling at line frequency is shown in Fig. 
31. A negative-going waveform is provided by the cathode- 
follower (video output). Tliis is coupled to the anode of a 



BASIC CIRCUITRY 



53 




PID. :;i. -Yhiox AM.r. < iu< lit with Diodk "Gate". 

" gating " diode to whoso cathode is fed a train of large, narrow 
pulses, also negative going. These ' : gating " pulses are in this 
system obtained from the line output transformer. They must 
ho narrower than the " back porch " period and must occur at 
tho centre of this period. If the timing is not correct, it is 
necessary to delay or to advance tho pulso train by some suitable 
means. The pulses must be larger in amplitude than the video 
waveform. Tho diode acts as restorer, and the tips of the pulse 
train are restored to the potential existing at the cathode of tho 
cathode-follower. This potential, if the timing is right, will be 
'he black level. If the signal strength should increase. I hen 
'he potential of tho restored pulso train will fall with respect 
i" earth, and vice versa. The voltage is applied to tho cathode 
" f \ 2. The bias on the grid of V2 is adjusted, by means of the 
'entrust control, so that the tips of the pulses just cause anode 
current to flow, thus producing a similar train of pulses across 
the anode loud. When the signal strength alters, and tho re- 
stored pulso train moves its potential with respect to earth, the 
pulse train in tho anode circuit of V2 alters in amplitude accord- 
ingly. This information is rectified, by means of the rectifier 
and smoothing components shown, so producing a D.C. control 
voltage. 

In some models the gated A.G.C. circuit samples the positive- 
going video waveform at the cathode of the vision demodulator. 
". I . tn tn ' s system, a positive-going gating pulse is required. 
'his has been obtained from the anode circuit of a line multi- 
vibrator, and by differentiation of the signal at the grid of tho 



54 



TELEVISION ENGINEERS' POCKET BOOK 




PULSE 
DELAYING 
CIRCUIT 



FlG. 



Siiowiso How thk "Gated" Arhanokmknt is Yiu. 
iNcniiroit.vncn is the lu:t ikjvhr. 



synchronising soparntor. In the latter caso tho A.G.C circuit 
has tho advantage- of being completely independent of tin- timu- 
bases. 

" Sync. Cancelled " A.G.C. 

A further common alternative A.G.C arrangemont, known as 
" sync, cancelled " A.G.C, is shown in Pig. 33. The video wavo- 
fonn, with positive-going synchronising pulses and negative- 
going picture information, is fed to tho anode of Dl. Negative- 
going synchronising pulses from tho synchronising separator are 
also fed to tho same point. Tho synchronising pulses are thus can- 
celled out and, through the D.C restoration action of tho grid 



VIDEO 
INPUT 



Fid. :;:;. cvimmuk lottii nx 
"8IBO. QiSCXUSO" 

Vl.SKiX A.G.C. 




BASIC CIRCUITRY 



55 



circuit of the synchronising separator, a waveform the most 
positive portions of which correspond to black level exists at the 
anode of Dl. Dl is a poak detoctor, and changes in tho black 
level result in a suitable bias voltage across Rl. 

A number of variations of these systems have boon used. One 
disod vantage of the arrangements described is that tho gain is less 
than unity. Several circuits have boon evolved to provide 

greater gain, though those have as yet. found little application. 

FLYWHEEL SYNCHRONISATION 
Fringe reception is often rendered more difficult by the line 
nM-illator being triggered by noise pulses reaching the oscillator 
just before the arrival of tho line-synchronising pulse, producing 
jagged vertical edges to the picture. Several systems have been 
developed in which the frequency of the lino oscillator is not 
controlled directly by the synchronising pulses but indirectly l>y 
means of b discriminator circuit which compares tho phuse re- 
lationship ln>i worn the line oscillator frequency and tho incoming 
synchronising pulses. Should the frequency of tho oscillator 
begin to " wander " from that of the pulses, the discriminator 
develops a control potential which modifies the capacitance of the 
oscillator circuit in such a way as to bring the frequency of tho 
oscillator back into step with the synchronising pulses. 

A common form of line flywheel synchronisation circuit is 
shown in Fig. 34. From this it can be seen that the synchro- 
nising pulses are fed, through u phase-splitter transformer, Tl. 
it> tho phase discriminator circuit, 1)1 and 1)2. A saw-tooth 
waveform, from the lino output transformer, is also fed to tho 
discriminator circuit. The integrated output is applied as a 
bias voltage to control the frequency of the oscillator. In some 
receivers a vulvo phuse splitter replaces Tl. A double diode, 
*i i eh as the KB91, may also be used in place i>( Dl and D2. 



1 




-2SV 



COMTROL VOLTAGE 
TO OSCILLATOR 



Pre. .;t. Ookhon flywukki, Stoohtwhobation QtRCCtr. 

Dl ANU \ri t'oltM A 1'IIASl-; HlsriUMINATim (,'lWftT. 



56 



TELEVISION ENGINEERS' POCKET BOOK 

L2°i_ JLAJL 



PULSES -< UU P 



-w- 



-II- 



lOOk; 



41^ 



■ — * *- 

i CONTROL VOLTAGE 

§ 22k TO OSCILLATOR 

51 



Fig. 33.— altbiinatiyt; vi.ywitki i. Synviiuomsatiox Cmoort. 

An alternative system is shown in Fig. 35. The synchronising 
input consist 3 of positive -going pulses, which are compared with 
a scries of short poises of positive and negative polarity derived 
from tho lino output transformer during the flyback period. 
A separate winding on the output transformer provides these 
pulses. 

The two circuits so far mentioned are suitable for controlling 
a line oscillator of tho cathode-coupled inuifci -vibrator type. 
Where the line generator is a blocking oscillator, however, the 
control voltage is applied via a reactance valve. A typical 
circuit is shown in Fig. 30, tho control voltage being derived from 
a discriminator circuit as shown in Fig. 34. 

A system using a different typo of discriminator is shown in 
Fig. 37, and has nlso been used in a number of models. In this, 
it pcnloile, VJ. aels as roineidenee detector. V I is biased so us 
in pass mi, amplified, only the negative portions of the differen- 
tiated synchronising pulses. These are applied to the screen grid 




I'li;. ::ij. l.'iv iam i-; \ ai.vk <\ l; < iixtkhluxi; 

.\ J!l,(>( K1NC Os< ».!,AT<ilt (V2). 



BASIC CIRCUITRY 



57 



Rl? 
!/OStO 



.TO LINE 
JC3 OUTPUT 
T 15 ^ I VALVE 




Fia. 37.- Flywhkel Synch kunisauob (,'utcuir Csimj a 
Co LS C 1 1) E X CB DBXH3TDB ( V2). 

of V2, a series of pulses corresponding to tho line flyback period 
I icing fed to the control grid. Tho mean anode current of V2 
varies with the phase difference between these two sets of pulses, 
a control voltage being developed at the anodo to control an 
oscillator, V3 and V4, of the uiiilti -vibrator variety. 

The cycle of operation of this system is 

(1) line-oscillator frequency falls; 
{2) line-scanning time increases ; 
(3) line-flyback pulse is delayed; 



IG. g& U a I PORUS \;- 

SOCIATKD WITH TUB 

pgtCTo oa ooinci ijkxi at 

DKTECTOJl FLYWIIKKJ. 
SYXCIIKONISA'HON Cilt- 
CUTT TK FIG. 37. 

(This diagram, and Fig. 37, 
'"■# reproduced fijr eonrtf.ii/ of 
Mallard, Ltd.) 




TCIODE ANODE 



fTTUi 

ttH 
jllllllu. 



PENTODE GRID 



UULULJU 



(j j 



58 



TELEVISION ENGINEERS' POCKET BOOK 




l''io. :;:». flywiikki. ^v.veiiJMXisvriMN ciun.-rr i.'simi a THooob 
OOSFABiXOB YaI/vk (Via). 

(4) degreo of coincidence between flyback pulse and 
synchronising detector is reduced ; 

(5) anode current of coitieideneo detector falls; 
(G) anode voltage of coincidence detector rises; 

(7) line-scanning timo fulls; 

(8) line-oscillator frequency rises. 

Far mi initial rise in ltne-oseillator frequency, the converse of the 
above stages occurs. 

A simpler form of flywheel synchronisation that has recontly 
become popular is shown in Fig. 39. This circuit is generally 
designed around a single double-triode valvo such as the E0C82 
or 12AU7. Vlb forms a saw-tooth generator, the frequency 
being roughly determined by L1-L2. The winding L3, con- 
tained in the sarno special can, which in appearance resembles 
;in l.K transformer, is resonated by the O-Oiu-fiF condenser to 
the line frequency and is excited into sinusoidal operation by 
mutual inductive coupling, and this helps to stabilise the oscillator 
frequency. The sine wave is superimposed on the normal wave- 
form at the grid of the oscillator, and the rosulting wave is applied 
to the grid of Via, which forms a control or " comparator " 
valve. This control valvo is biased so that only the tips of the 
sinusoidal peaks arc conducted. .Simultaneously, to the cathode 
of this valvo is applied the line-synchronising pulses, of negative 
polarity. The composite pulse, consisting of tho peaks of the 
sinusoidal lino -frequency element and the amplified line-synchro- 
nising pulses, appears in i he cathode circuit. The duration of the 
composite pulse, and hence tho averago current passing, depends 
upon the phase relationship of tho two waveforms, and by in- 
tegrating the current pulses a potential is built up across tho 
0-01-jtJ? condenser proportional to the duration of the pulses — 
a longer pulso being passed by Via when the time-base generator 



BASIC CIRCUITRY 



59 



is running slow compared with the incoming synchronising pulses, 
and vice versa. This potential is then used to control the speed 
of Vlb by varying its bias. The 100k, 001 -pF and 4*7k, 0-5«pF 
components form an " anti -hunting " network by providing a 
long time-constant in tho cathode of Via. A moderate change 
of oscillator frequency can also bo effected by shifting the cut- 
off point of Via by altering its anode voltage, and this fact is 
made use of to provide a line hold control, 

TYPICAL CIRCUITS 

In Figs. 40-43 are shown four complete receiver circuit 
diagrams. These have been selected to show typical circuit 
practice in the main types of receiver that have been produced — 
i.e., T.R.F., Band I superheterodyne and Band I /III superhetero- 
dyne receivers. 

The circuit in Fig, 40 is of a stagger-tuned T.R.F. receiver, 
with thyratron time-bases and 12-in. picture tubo, of tho typo 
common up to 1951 . Fig. 4 1 shows a 17-in., five-channel receiver 
typical of those produced just before the commencement of the 
I. T. A. transmissions in Band III. Figs. 42 and 43 are recent 
Band I/III models, the receiver in Fig. 42 (with turrent tuner) 
being intended for service-area reception and that in Fig. 43 
(with incremental switch tuner), incorporating an elaborate, 
gated A.P.C. system and lino-flywheel synchronisation, being 
intended for fringe reception. 

A list of the valvo functions in each receivor is given bolow. 



Valve Functions, Circuit Fig. 40 

vi 

V2, V3, V4 

V5 



Vision and sound R.F. amplifier 

Vision R.F, amplifiers 

Vision detector and peak amplitude clipper 
(interference limitor) 
Vli . , Video amplifier 

V7 . . Sync, separator 

V8 , . t-'rumo interlace diodo 

V!), V10 . Sound R.F. amplifiers 

VII . . Audio amplifier (triode), sound detector and 

interference limiter (follower type) (diodes) 
V12 . . Audio output 

VI 3 , . E.H.T. rectifier 

V14 , , Line generator (thyratron) 

V15 . . Line output 

V16 . . Frame generator (thyTatron) 

VI 7 . . Frame output 

Via . . H.T. rectifiers 

V20 . . Picture tube 

Tho controls are as follows: VR1, contrast; VR2, focus; 
VK3, brilliance; VR4, volume; VR5, line hold; VR6, width; 
VR7, frame hold; VR8, height; L14, VK9, line linearity. 



60 



TELEVISION ENGINEERS' POCKET BOOK 




Fit:. m.- Ciui-iut l »i At; ham dv \ t.i ;.l-". 



BASIC CIRCUITRY 



61 




Ji '*KIVKH WITH TltYHATIlOS TIMK-IIASKS. 



62 



TELEVISION ENGINEERS' POCKET BOOK 



Valve Functions, Circuit Fig. 41 



VI 
V2 

V3, VI . 

V5 
V6 
V7 



V*8 

v»i 

VIII 
VI I 
V12 



R.F. amplifier, sound and vision 
Frequency changer (self -oscillating mixer) 
Vision I.F. amplifiers. These aro followed by a 

germanium diode detector. 
Vidro amplifier 
Sync, separator 
Frame interlace (pentode triode-connected) and 

half line multi-vibrator (triode-output. stage 

forms other section of multi-vibrator) 
bine output 
Efficiency diode 
K.H.T. rectifier 
Sound I.F. amplifier 
Audio amplifier (pentode), detector and sound 

A.G.C. (diodes) 
Sound and vision interference limiters 
Audio output 
Frame blocking oscillator {triode) and output 

(pentode) 
H.T. rectifiers 



VI 3 
V14 
Via 

VI 6, V17 

The width control in this circuit takes the form of a variable 
inductor in parallel with u section of the lino output transformer. 
Frame linearity correction is provided for by means of the 25k 
potentiometer in l lie feedback loop in the frame time-base. The 
Iratne output valve. VI 7. is resisfance-eapacitaaoe coupled to the 
frame deflection coils. K.H.T. is about (i-fi kV. a figure typical of 
!» and \2 in. models of this period. The four R.F. vision Stages 
were aligned to the upper sideband in order to improve separa- 
tion between vision and sound ehanneb. An antu-i i ansi'onncr is 
arranged to supply some 300 volts r.ni.s. to the H.T. rectifiers. 

Valve Functions, Circuit Fig. 42 

VI 
V2 
V3 
V4 

v;> 



vo 

V7 



V8 

V9 

VIO 
VI I 
V12 



Cascode R.F. amplifier 

Frequency changer 

Common vision and sound I.F. amplifier 

Vision I.F. amplifier 

Vision detector (A section) and frame sync, pulse 

Shflp' I ; -.■■i'i: ■■: 

Video amplifier 

Syne, separator (pentode) and half line multi- 
vibrator (triode-output stage forms other 
section of multi -vibrator) 

Frame blocking oscillator (triode) and output 
(pentode) 

Sound I.F. amplifier 

Audio amplifier (triode) and output (pentode) 

bine output 

K.I I .'!'. red ilier 



BASIC CIRCUITRY 



63 




64 



TELEVISION ENGINEERS* POCKET BOOK 



BASIC CIRCUITRY 



65 







T f T" i 



i I" 



MS ~ 



S. (U ± hm J 






Fm. i2. oatcun duobam oi a Baud i hi 

VI 3 , . Efficiency diode 

VI 4 . . H.T. rectifier 

V 1 5 , . Picture tube 

Vlfi , . Sound detector and interference limiter 

MR1 . . Vision A.G.C. delay diode 

The controls are as follows: VTU, contrast; VR2, frame hold; 
VK3, height; VR4, line hold; VRfi, frame linearity; VR6, 
volume; VR7, brilliance; L22, width; L2S, line linearity; 
TCI, fine tuner. 

Frame fiyback suppression is appliod via 035. Mean level 
A. P.O. is us. a. 

Valve Functions. Circuit Fig. 43 

VI . . Casnodo R.F. amplifier 

V2 . . Frequency changer 

V3, V4, V5 . Vision I.F. amplifiers 

V6 . . Vision detector 




IIKI'KLVI'.K WITH TURRET TUSEH. 



V7 

V8 

V9 

V10 
VI 1 
VI 2 

via, 

Vlfi 
V17 
Vis 
V19 
V2l> 
V21 
V22 
V23 



V)4. Vir, 



Video amplifier (pentode) and cathode follower 

output (triode) 
Vision interference limiter (black -spotter type) 

und A. P.O. amplifier 
A.P.C. gate (triode) and sync, separator 

(pentode) 
A.P.C. rectifier 
A.P.C. delay diode 
H.T. rectifier 
Sound I.F. amplifiers 
Sound detector 
Sound A.G.C. delay diode 
Sound interference limiter (follower type) 
Audio amplifier (triode) and output (pentode) 
Frame interlace diode 
Frame multi-vibrator 
Frame output 
■' Flywheel " line sync, phase discriminatora 



66 



TELEVISION ENGINEERS' POCKET BOOK 



BASIC CIRCUITRY 



67 



i I 




I 



3" 




V24 

V25 
V26 
V27 



>'i<i. 43.— Circuit Diagram of a TimnKKN-ciiANNi Bi 

Line multi-vibrators 
Lino output, 
Efficiency diodo 
K.H.T. rectifier 



T 



f^ F«rn — p«n — n — j — r^" f^ 




Uomhi with Gated a.Q.C. and " flywheel " Satcmsasmstas. 

V28 . , Picture tube 

V29 . . A.P.C. protection diode 

Frame flyback suppression is applied via.C89, R109 and HI Vt 
lo the cathode ol' tin- picture tube. 



[SECTION 4 J 
COLOUR TELEVISION 

Sevs&AIj series of experimental colour television transmissions 
havo been radiated, since 1955, by tho B.B.C. from its Band I 
London transmitter at Crystal Palace. These transmissions, 
which have included live studio productions and films and slides 
from a colour television studio and control room at Alexandra 
Palace, usually take place after the close of the normal trans- 
missions and during the afternoons. 

These experimental transmissions do not commit the B.B.C. 
to the adoption of any particular system of colour television. 
The decision whether or not to introduce a public service of 
colour television, the starting date and the system to be adopted 
rests with the Postmaster-General. 

A colour television service was introduced in tho United 
States in 1954, and there have been conflicting viows expressed 
on the results achieved, although more than half of tho total 
number of transmitting stations are equipped for radiating 
colour transmissions. A U.S. table colour receiver costs about 
£180 with a comprehensive service charge of about £33 a year. 
Receiver sales have not been as great as was originally predicted, 
but nevertheless exceeded 150,000 in the two years following 
the introduction of 21-in. colour tubes. 

It seems most probable that some form of public colour service 
will eventually be introduced in the U.K., and, since the servicing 
and maintenance of colour receivers present many new and 
complicated problems, it is important that television engineers 
should be aware of the main lines of development in this field. 

AH practical colour television systems are based on the physi- 
ological fact that the sensation produced by most of tho colour 
encountered in real life can be reproduced using only three 
colours. At the transmitting end the scene is analysed by 
optical filters in terms of the amount of rod, green and blue light 
present in each picture element. At the receiving end the scene 
is reproduced by the combinations of separate red, green and 
blue lights having characteristics corresponding to those of tho 
analysing filters at the transmitting end. 

Sequential Systems 

Several different colour systems have been developed, and it 
is by no means certain which will eventually be adopted. For 
example, the basic sequential system, using rotating colour discs, 
each comprising, say, six gelatine colour filters and rotating at 
about 1,500 r.p.m., has been developed from the original Baird 

88 



COLOUR TELEVISION 



69 






experimental work and is the method commonly used for closed - 
circuit work. In order to obtain a picture of comparable details 
and flicker to that of black-and-white television it is necessary 
to increase the frame-scan and line-scan frequencies by about 
three times that required for monochrome work. The trans- 
mission of picture signals would thus require a very large band- 
width, which, in practice, would make it necessary for the 
transmitters to operate in Bands IV and V. Also such trans- 
missions would not be " compatible ", which is to say that the 
colour transmissions would not be reproduced on an existing 
type of receiver as black-and-white pictures. A sequential 
n'ystem which is compatible, and which is in many ways similar 
to the N.T.S.C. system discussed below, has been demonstrated in 
France and has the advantage of considerably simplifying 
receiver circuitry. 

N.T.S.C. Systems 

The system which has been used in the B.B.C. tests is based on 
the American N.T.S.C. (National Television System Committee) 
•system, but is modified to meet the requirements of the British 
Hi.l-line, positive-modulation standards. The system is fully 
" compatible ". Two signals are transmitted simultaneously, 
one the luminance signal, which contains the picture brightness 
information, and the other (transmitted as a sub-carrier) is the 
chrominance signal, which contains the colour information. By 
a system of frequency interlacing the colour signal does not 
interfere with the brightness signal, and allows the band-width 
nl tho full transmission to be kept within the normal vision band, 
i tins allowing transmissions in Band I and Band III, etc. Tho 
colour information transmitted on the sub-carrier consists of 
hue (e.g., red, brown, yellow, purple) and its saturation, that is 
to say the purity of tho hue as opposed to its dilution with white 
light. When these signals are picked up by a black-and-white 
receiver the luminance signal gives a normal black-and- while 
picture, the chrominance signal producing no visible effect. On 




Fhj, i, N.T.S.C. CoLOxm Television Wavefohm. 

(a) Idealised overall transmission curve; (ft) line-sync, pul3e. 



70 



TELEVISION ENGINEERS' POCKET BOOK 




SYNCHRONOUS 
DETECTION 
OSCILLATOR 
CONTROLLED IN 
FREQUENCY & 
PHASE BY 
"BURST" 



BANDPASS 

FILTER 
TWToSMc/s 



QUADRATURE 
NETWORK 



r DEMOWLATWI 



DELAY TO 

TIME ufiTH 

Q 






FlO, 2.- HLOCK DI ACEAM FOR A RRCKTVEft FO« TI1K 
A'.T.S.O. BXSZB8 TRANSMISSIONS. 

a colour receiver both signals have their part to play, in order 
to produco the desired colour. The incoming signal passes in 
in normal manner through the R.F. and I.F. stages. Alter 
the demodulator, however, the signal is fed into tho brightness 
channel, corresponding to the usual video channel, and modulates 
simultaneously the three grids of a tri-colour cathode-ray tube. 
The demodulated signal is also passed through a band-pass Biter 
in order to separate the colour information from the brightness 
signal. Then, by a synchronous detection system in which the 



COLOUR TELEVISION 



71 



PHOSPHOR DOTS 
<=■ 10* TOTAL) 



AREA OF WASTED 
ELECTRONS DUE TO 
OVERSIZED BEAMS 



DIRECTIONS OF 
ELECTRONS IN 
THE 3 BEAMS 




, ^ — -TUBE SCREEN 
(VIEWED FROM GUN SIDf) 



-SHADOW MASK 



HOLES (> 4 * 10* TOTAL) 



3 ELECTRON BEAMS 
FROM 3 GUNS 



I-'Ki. :!.— SCHEMATIC DIAGRAM OF A TllUKK-HKAM, 
SIIAIM.IW-MAKK ClU.fiCH l'liTISUK 'i'UHK. 



signal ia heterodyned with two sine waves having the same 
frequency and the phase as the component to bo extracted, two 
colour-difference signals are obtained. Subsequently, by means 
of an adding circuit, a third colour component is derived. The 
three colour components are then fed to the three cathodes of 
tho tri-colour cathode-ray tube. 

There are several methods of locking tho receiver synchronous 
detection reference oscillator in frequency and phase to a refer- 
ence signal. The crystal and automatic feedback loop is a good 
example. The reference signal consists of a " burst " of eight 
cycles of a sine-wavo of sub-carrier frequency and phase trans- 
mitted in each post line-synchronising suppression period. The 
amplitude of the " burst ,; sine-wave is halt" the magnitude of the 
synchronising pulses, with the mean value at black level. 

In the tri-colour cathode-ray tube three soparate beams come 
from independent cathodes within a three-beam shadow-mask 
picture tubo (developed by R.C.A.). The 21 -in. R.O.A. tube 
contains a screen of 400,000 groups of throe colour -fluorescing 
dots of phosphor. The three dots in each group produeo red, 
green and blue light respectively, and the three olectron beams 
coming from its own gun are so directed through the shadow 
mask that each beam falls upon only one dot in each group. 
There aro thus effectively a red, a blue and a green gun operating 
simultaneously, while the patches of light produced by the throe 
beams subtends such a small nngle at tho observer's eye thai 
each beam is not separately distinguishable. 

An alternative system of reproduction is to produce three 
separate images on three separate projection -type cathode- raj 
tubes having red, green and blue screens and then to combine 
the images optically by means of mirrors. An advantage of 
this system is that it overcomes the high cost of replacement 
aasociated with the tri-colour tube. 

The development in the United Kingdom of Dr. Gabor*s 

Hut. " cathode-ray tube may eventually simplify colour display. 

Subjective Colour System 

Considerable interest has been shown in a proposed system 
based on the use of only tiro simple signals carrying colour in- 
formation, investigated in the United States by Dr. B, H. Land. 
The system depends for many of its colours upon subjective 
effects, believed 1" occur in the brain, whercbv l lie viewer receives 
'lie impression of colours which are not actually present, in the 
received picture. " White " may be used as one M colour " 
component, while a red channel, for example, could he used for 
the other signal. While a considerable measure of agreement 
;| s io the subjective effects has been shown 10 exist between 
different observers, it is generally believed that, at the present 
Stage of development, a television system based on pictures using 
this technique would have a most limited range of chromastieities 
compared with, for example, the more complex N.T.S.C. system. 



72 



TELEVISION ENGINEERS' POCKET BOOK 



Experimental Colour Receiver 

A typical experimental British colour television receiver, 
measuring 2 If X 28| X 31 f in., developed by the General 
Electric Company, uses 35 valves and a 21 -in. B.C. A. shadow - 
mask picture tube. 

The receiver power pack incorporates direct rectification of the 
mains supply to provide one H.T. line of 250 volts at 200 itiA, 
and a second H.T. line of 450 volts and 400 niA is obtained by a 
voltage-doubling circuit. A stabilized negative line of - 150 
volts is also available for bias supplies. 

The tube E.H.T. supply of 23 kV at 1 niA is obtained directly 
from the line flyback without voltage doubling, and a triode shunt 
regulator is used to stabilise the K. H.T. ami I hereby minimise 
the effect of E.H.T. changes on the convergence of the three 
electron beams. 

Passive convergence circuits are fed from the line and frame 
time-bases and supply the appropriate current waveforms to i he 
dynamic convergent coils mounted round the neck of the tube. 
Direct currents are also applied to these coils for static con- 
vergence adjustments, and all the preset convergence controls 
are easily accessible at the front of the receiver. Line and frame 
raster shift is controlled by D.C. injection into the scanning 
coils. 

On the signal side a standard H.V. switchahle tuner feci Is a 
slightly modified prod net ion type I.F. deck. Wound rejection 
and sound l.F, take-off conform to usual monochrome practice, 
but in the vision circuits two separate crystal detectors ((! KX54's) 
are used to provide isolation between the luminance and chromin- 
ance channels. This arrangement enables a high-definition 
luminance signal to be maintained, and when this is fed to the 
fcrrite-luaded delay line (to provide time coincidence of luminance 
and chruiuinuneei small reflect ions in the line aro prevented from 
<list orbing the smooth and symmetrical chrominance channel 
f'requeiiev response. 

The luminance signal is amplified by two video si ages in a 
' ; boot-strap " circuit and is ultimately fed in the correct drive 
ratios to the three cathodes of the tubo. Master brightness is 
controlled b\ a bias arrangement in one of the video stages, nod 
the D.C. component of the signal is maintained to within about 
1 db. 

Two chrominance amplifiers with a 6-db band-width of ±500 
ke s supply two " clamping " trindes for high-level demodulation 
along the red and green difference axes, R— Y and G-Y. After 
filtering, these difference signals are fed to the red and green 
grids of the tube, and also to a matrix amplifier which forms the 
B- Y signal for the blue grid of the tubo. A reference frequency 
amplifier provides the two appropriately phased reference signals 
for the triode demodulators, 

A front-panel chrominance-gain control is provided for 
adjustment of tho colour saturation. 



COLOUR TELEVISION 



73 









Kin. 1. Tool. Kirs i-'ou 

SBKVTCH KNinSKKHS. 

Tins tool wallet (feype f) Is 

one Of -ovcr.'d kits of tools for 

mil in ;tn«l teteriaton service 
engineers marketed hy Philips 
KlectricfU Ltd. it ootitaiitt 
the following tools: general 
purpose pliers u'iwiUiumIi; 

pointed nOBO pliers (insul- 
in reil); side miters (insu- 
lated); mnlti-pnrposi! trim- 
ming tool; tweesers; iont- 
|-ii fit screwdriver luuujlc with 
r.lirr-e iloiihle-oiiili-d screw- 
driver slmnks (for slotted 
and eross-ottt uerews); off- 
nei icrewuriver; nod volt:ige 
ii ~iii L'rnii Mtrewdrlver. 




The continuous reference signal required for synchronous 
demodulation is obtained from an L.C. oscillator, which is 
frequency and phase locked by a two-mode A. I'.C. loop, or D.C. 
(juadri -correlator. 

One of the two detectors in the A.P.C. loop provides a D.C. 
voltage only when a burst signal is present and when tho oscillator 
is phase locked. Since this is a synchronous detector, it provides 
an accurate indication of the presence of a burst even under 
adverse signal -to-noise conditions, and is used as a colour 
" killer " control for switching off the chrominance channel 
automatically when a burst signal is absent. The output of this 
detector is also fed as an automatic chrominance control or 
A.C.C. signal to bias the chrominance amplifier from which the 
hurst output is taken. 

The colour burst is separated from the chrominance waveform 
and amplified before being applied to tho A.P.C. detectors. The 
separation is carried out by a gating circuit which switches on 
'be burst amplifier only during tie' burst period of about 4 micro - 
seeonds. In order to be quite independent of line time-base 
synchronisation, the gating circuit operates from the back edge 
of the Itne-sypphmnising pulses appearing in the synchronising 
separator output, 



[SECTION 51 

TRANSISTORISED RECEIVERS 

The first portable transistorised receiver operated from either 
batteries or mains supplies and using 21 transistors and 1 2 crystal 
diodes for all stages except E.H.T. rectification war marketed in 
the United States by Philco during 1969. An 8-in model was 
marketed in .Japan in I960. Experimental models, including a 
Milliard design, have been demonstrated and rioserihed (Journal 
of the, Television Society, Vol. H, No. 11, liloS) in the United 
Kingdom . 

The main technical problems involved with transistors are : 
( 1 1 the V.H.F. front-ends and I.F. strips ; (2) the provision of 
sufficient video frequency output; and (3) line scanning power 
requirements. 

Tlio practical solution of (1) has become possible with the 
development of transistors such as alloy diffusion and surface 
barrier types, having good performance characteristics extending 
well into the V.II.K. range, and it is now possible in design 
satisfactory vision and sound receivers, Tho American Philco 
model has four vision I.F. stages stagger toned around \~> Me s. 
The Mm Hard receiver used five stagger-tuned vision l.V. stages 
on a I )uiii 19 Mc/s. 

Problems (2; and (3) would be simplified by tho development 
of transistors which would withstand high collector potentials. 
For (2) it is difficult to design a transistor video amplifier provid- 
ing u peak-to-peak output of tho order of S(i volts as required for 
a conventional picture lube. The Milliard design, which used a 
standard type of tube, had a '' beanstalk " video amplifier with 
five transistors. An alternative solution is to be found in 1 1 n- 
development of high-elope picture tabes requiring less video 
drive. 

Scan Magnification 

One method of reducing the power requirements for line 
scanning, adopted in the Milliard design, is Ute use of a 
magnetic scan magnificat ion system capable of providing a power 
saving of" about UK): I for the line time-base and about 4: 1 
for the frame time-base. This is based on a magnetic focusing 
system which magnifies the scan defloction as follows : 

IT an electron path is through a fixed magnetic Held having 
opposite sense on either side of the cathode-ray-tube axis between 
the deflection assembly and the screen, (ben the deflection angle 
of the beam can be increased in a manner analogous loan optical 
lens. Normally, however, with such an arrangement the deflec- 

74 



TRANSISTORISED RECEIVERS 



75 






tion in a plane at right angles to tho plane in which there is 
magnification will be decreased. However, if tho field strength 
of the magnifying lens is increased beyond a certain point the 
scan in the second plane is also magnified, though with a reversal 
of sense. Simply interposing a magnifying lens would, however, 
increase spot size as well as the deflection angle, so that little 
benefit would bo obtained. This difficulty can be overcome by the 
use of a quadrupolo focusing system, comprising a pair of quad- 
rupole magnet assemblies spaced a short distance apart along 
the tube neck, and having diverging planes set at 90° relative 
to each other. Adjustable magnifying lenses have been de- 
\ eloped which overcome deflection dofoeusing by the use of poles 
shaped as equilateral rectangular hyperbola', and which retain 
a gootl raster shape. To maintain focus in the horizontal direc- 
tion when the beam is deflected vertically there are additional 
correction windings, energised by tho frame time-base, on the 
deflection yoke. It should be noted that the final focus is more 
sensitive to E.H.T. variations than a conventional system. 

The Milliard receiver used a separate stabilised E.H.T. generator 
based on two Of Hi power transistors in a square-wave 4Uf)-c's 
oscillator circuit and a voltage-douhler rectifier circuit providing 
some 18 kV stabilised to within ±0-3%. 

Optical Magnification 

The American Philco receiver overcomes deflection power 
problems largely by the use of a 2- in. Lube and an optical magnifi- 
cat ion system which provides a virtual image- some 7 K times 
thai or the real image, to provide a 1 1 -in. x 8] -in. picture. The 
virtual image appears to lie placed several feel behind the sol, 
and a front visor is used to permit viewing in sunshine. Tho 
optical system is shown in Fig. 2. The light from the 2-in. tube 
is projected on to a two-way mirror termed a " beam splitter " 

which reflects the light and vol is l-rnnspnrenl to the viewer, 
This minor is mounted above the picture tube and directly 
behind tho viewing aperture. The light- from the tube is re- 
Beoted by the two-way mirror on to a spherical mirror. The 
effect of the spherical mirror is to produce a virtual image appear- 



1 '<■- 1. OlTfCAt. M\»;m- 

ncATioH system uhbA 

OS 1'lUl.tX) TKAXSIS- 
TORISF.ll ItKCKIVKH. 




2" PICTURE 
TUBE 



76 



TELEVISION ENGINEERS' POCKET BOOK 



ing magnified behind the set when viewed through the beam 
splitter mirror. 

In this design the S)-kV E.H.T. is obtained with a voltage- 
doubler using two thermionic rectifiers from a line flyback 
system. 

Power Supplies 

The experimental Milliard receiver operated from a 12-volt. 
silver-zinc rechargeable battery with a total power consumption 
of 12 watts. The Philco model, which weighs 1,5 lb,, and 
measures 8j in. X *t in. x I fig in. high, operates from either 
A.C. mains or an internal hattery which is rechargeable from ;in 
internal battery charger. It is claimed that each battery can 
he recharged 20 times and provides 4 hours service for each 
charging. The receiver cost is about £8!), and the batteries a 
little under £2. The Japanese " Sony " 8-in. -model, which 
weighs 13 lb,, can nlso be Operated from mains supplies or 
batteries. 

TRANSISTOR D.C. INVERTERS 

The operation of conventional television receivers from low- 
voltage D.C. sources, such as car batteries, has until recently 
required either some form of rotary conversion machine or a 
high -win I ;)(.'<' vibrator unit, A new form of electronic conversion 
has become possible with the development of power transistors 
capable of switching relatively high currents. 

In order to achieve D.C. in A.C. conversion, the steady direct 
current must, bo " chopped " h'to a repetitive series of pulses 
which can subsequently he stepped up to any required voltage 
by normal transformer action. In a vibrator unit this chopping 
(m- switching is done mechanically. In a transistor converter 
the transistor acts as an electronically controlled " on-off " 
switch. A junction power transistor can form an almost ideal 
switch : when the transistor is " off " only the very low collector 
cut-off current flows ; when " on " it behaves as a low resistance. 
By being made to oscillate, the transistor automatically varies 
between these two conditions, and can thus be used to interrupt 
a D.C. source. 



INPUT 
24 V. 
D.C, 



H p r^ 1 y s-| 



^p p^3 




Fih. 2.— Tiunsistok D.G, OOMVWenH Sutaiij.k for oppnyrmx o*' 
Ti-i-ICVislox BECHmtttS, 

Yqlradfa J.iil.) 



TRANSISTORISED RECEIVERS 



77 







i Hi. :;. THA.Nsisi'imisiai 
sxxnsam Bquirtmst. 

Transistors haws miwle po»- 
gible oompact poeke&sfaed 

-; instra ate with aegtig- 

iiilu battery orate, IWa r 

■ : :!.i >; 1J in. reaisstwii'C- 
capacltaaoa bridge, weigh* 
only about 12 «/,., and mea- 
sures capacitances of 3 iiF t« 
'.'ii (jV niul rn-Ui :i:n-i:- in.'Ti i 
.". ..Inns to 20 MQ. 

' i,niiii)i Electronic Industries, 
/ML) 



Although the above action forms the basis of all transistor 
converters, there are a number of possible circuit arrangements, 
including the " ringing choke " for low -wattage application, and 
the push pull transformer-coupled circuit for medium-power 
work. For high-wattage requirements, such as the operation 
of a conventional television receiver, a suitable circuit is the 
polarity changer arrangement shown in Fig. 3, using four (or a 
multiple of four) power transistors. The representative unit 
shown provides a maximum output of the order of 200 volts at 
U'6 amp. from a 24-volt D.C. source. 



9m. I. v.u.vk 70UBOKSB Krr. 

The cuiisLruuLiuii of liijjli purfonn- 
■ iiirr< u;sr instruments by service 
eogtoeem— et an appteciableaaviiigln 
'■'ist, comparad wfth Eaetory imili 
■Miulpmenl bu been greatly sim- 
plified i)v llic nee <»f printed cironft 
wiring panels, Tliit- Hrattikit vulro 
voltmeter, utilising a Rett plated, 
copper-foil printed panel, measures 
:i.c. volts (r.iu.s. and peak-to-paak), 
''■<■. mlrs, resistance (to lain) meg- 
"|im,s) and decibels fnem centre scale). 

Hie inpm impedance U II inegoliiiui 
and ii lias n-lj in., gijti jiA movement. 

\n tt.F. probe is availnhlc for u-se up 
to Inn l&cfa iiHalili' Indication to 

(Doffsttvm IU.) 




[SUCTION 6] 

PROJECTION TELEVISION 

Tvvu distinct methods have been employed for obtaining large* 
screen television pictures. The first method is by the use of 
special cathode-ray tubes having the viewing end of the tube 
in largo dimensions, e.g., 24 in. wide, the second method is by 
employing a small -diameter cathode-ray tube, giving a brilliant 
picture, which is then reflected from the end of the tube through 
a suitable optical system on to a large screen. This latter 
system is known by the designation " large-screen projection 
television ", It can be divided into three main types. 

The Hack Pun, miction System for domestic receivers, in 
which I Ik- optical unit is situated behind the screon, the latter 
being of ground glass or some other suitable translucent material. 
This method has been used in the Philips, and a number of other 
manufacturers' large-screen projection sets. 

Tin; Front Projection [System for domestic receivers. In 
this case the screen is soparato from the receiver unit, and an 
optical system is used to project the enlarged picture on u screen 
of high reflective power suspended on a wall directly facing the 




Fhi. L— araroxRSTS or tmi; Ml-llakh I'iumhtkis TiiLtvi* 
78 



PROJECTION TELEVISION 



no. 2.— Basic PRixciru-: 09 the Sciimiot unreal. 

System. i v 

The splierieril tuirror U the innln focusing element. 




79 



S — 



lens of the receiver. This is the system employed in the Deoca 
unci Philips large-screen front- projection receivers. 

I.ahge-sckeen Projection suitable for cinemas and theatres. 
This employs the ordinary Schmidt optical system, whereas 
the systems abovo employ the Schmidt " folded optical " system 
using piano reflecting mirrors. 

THE SCHMIDT OPTICAL SYSTEMS 

It will bo appreciated from tho above notes that two important 
items in any system of projection television aro tho special typo 
of cathode-ray tube employed and tho optical projection system. 

The Direct System. The Schmidt- optical system is shown 
in its simplest form in Fig. 2, in which it will be seon that 
light from an object in tho focal plane of the mirror is reflected 
hack through a correcting plate or lens, the purposo of which is 
i<> eliminate spherical aberration. 

Fig. 3 shows how this principle can be applied in a television 
projection unit. From this it will be seen that tho high-intensity 
tube is arranged co-ax ially with the spherical mirror, the position 
of the tubo along tho axis being adjusted during practical tests. 
Tho light emitted from tho fluorescent screen of tho cathode-ray 
tube is reflected by this mirror, and passes through the correcting 
plate or lens on to the scrocn of the television receiver. The 
hole at the centre of tho mirror serves a double purposo. First, 
if tho mirror had no aperture, most of the light failing on the 



AIR-COOLED 
SCREEN 




Fiu. 3. -jjciiiiiitr OrncAL Systkm afpuku to Phujkction Truevision-. 



80 TELEVISION ENGINEERS' POCKET BOOK 




PROJECTION TELEVISION 



81 



centre portion would be reflected back on to the face of the 
projection tubo, with a consequent blurring of the image. 
Secondly, the aperturo allows for the air cooling of the tube face, 
should this be found desirable with high-intensity tubes. 

The " Folded " System. In the " folded " version of the 
Schmidt optical system, which is shown in Fig. 4, the cathode -ray 
tube C projects through a central aperture in a mirror E, which is 
inclined at an angle of 45° to the axis of the spherical reflector. 
The inclined mirror K catches the light from the spherical 
reflector and directs it through the correcting lens X on to a 
second plane mirror G, from which it is again reflected on to the 
projection screen. 

CATHODERAY TUBES FOR PROJECTION SYSTEMS 
Tubes for Large-screen Projection 

Tho projection tubes used for large -screen television equip- 
ment have an anode voltage of 50-80 k V. Tho average beam 
current is 1-2 mA with a peak value of 15 mA, the cut-off and 
drive voltages being respectively minus 500 and plus 400 V. A 
high-frequency vertical oscillatory motion is imparted to the 
beam to produce " spot-wobbling , as it has been found that this 
increases the brightness of the picture and eliminates field line 
structure. Tho diameter of the face of the tube is 9 in., and the 
outer surface of the tube face is cooled by a current of air blown 
through tho centre aperture of tho spherical mirror. A magnetic 
focusing coil is used ; the deflection system also employs magnetic 
coils. An eight-pole magnetic field is used for correcting pin- 
cushion distortion of the picture. 



Tubes for Domestic Projection Receivers 

Those receivers employing the folded optical system use a 
smaller picture tubo. The following notes refer to the Milliard 
type MWlii, which has a screen diameter <if 2i in., and which is 
designed to operate at an anode voltage of 25 kV. At a beam 
current of 100 /iA, the spot size is 170 ft (0-0068 in.). The tube 
is quite conservatively rated and can. if necessary, pass higher 
peak currents. The spot size is then somewhat increased, with 
the consequent reduction in picture definition, but, as this 
current corresponds to peak white, slight loss of definition can be 
tolerated. Tho design of the electrode assembly is, of course, 
governed mainly by tho consideration of beam size. The re- 
quirements are that the beam must be of such dimensions as to 
produce a spot of tho required diameter, yot not so concentrated 
that mutual repulsion of the electrons produces blurring of the 
spot. Further, the beam at its widest diameter must be small 
enough to koep the electrons well clear of the tube walls and the 
anode when fully deflected. Finally, the I a !V e curve must bo 
sufficiently steep to allow tho tube to bo driven by a normal 
video-output valve. 

A sectional drawing of the tube is reproduced in Fig. 5. A 
spark trap, consisting of a ring-shaped electrode, is situated 
between the grid and tho anode, and is connected to ono of the 
base pins, which should, in turn, bo connected to chassis. Any 
discharge which might occur, duo, for example, to tho release 
of a small amount of gas as tho result of unintentional overload, 
will take place between i !■•- anode and tin* spark trap, thus avoid- 
ing damage to tho cathode. 

The external surface of the neck and cone is coated with a 
graphite preparation, and must be earthed. This coating, with 
tho glass envelope and tho internal metallising of the tube, 
forms a capacitance of approximately 450 pF which, with a 
1M resistor in the 25 kV lead, serves as the final smoothing for the 
E.H.T. supplv. 

Tho most conspicuous external feature oi the tube is tho glass 
shield surrounding the anode terminal. This shield obviates 
risk of flashover or leakage between the K.H.T. connection and 
the deflection coils or the graphite coating. 

The luminescent screen is backed by a metallic coating. 




Klli. 5.- -SKCriOXAL DUAWIN'U OP THE MVIJ-AUU MWlj-2 CATIIODK-HAY TUBS 
FOR PIUIJKCTION TELEVISION. 



82 



TELEVISION ENGINEERS* POCKET BOOK 




Fig. i!.— ViuKo olti'ut Stack Vsist: BF80, 

Compensation for Pin-cushion Distortion 

An optical system incorporating a spherical mirror introduces 
a certain degree of pin -cushion distortion, which, in the Milliard 
projection television system, is compensated in the design of the 
deflection coils. 

CIRCLTITIIY 

When it is intended to incoporato a projection unit in a tele- 
vision receiver, there are several points in I be circuit and general 
design which should bo borne in mind. 

Video Drive 

By using cathode compensation, it is possible to use an EF80 
B.F. pentode in projection video stages quite satisfactorily. A 
suitable circuit is shown in Fig. fl. This circuit has a high-value 
cathode bias resistor (820 ohms) and a high value of anode load 
(13,500 ohms). With this load resistance a current swing of 
only 6-3 mA is required for 85-V output, and this arrangement can 
he used because of the high feed-back factor provided by 
the cathode resistor. 

The ideal cathode resistance for feed-back purposes is a little 
too high for bias purposes, and a correcting positive bias (0-9 V) 
is applied to the grid through resistor HO. The demodulator 
and interference limiter are also shown in Fig. 6. 

The potential drop across the anode load under quiescent 
conditions is approximately 55 V, and the maximum swing from 
the H.T. line may therefore be in excess of 155 V. For this 
reason the anode must, bo fed from an H.T. line of at least 
275-300 V, and preferably 350 V. 

The video stage shown in Fig. has a gain of approximately 
11-5, so that the last I.F. stage and demodulator must be capable 






PROJECTION TELEVISION 



83 



of delivering at least 10 
V peak -to- peak to the 
video stage. 



' , 3O/i/F(A5&0MtO') 




-0*350V 



OC»T CAT NODE 



Video Drive Using PL83 

Where it is required to 
take full advantage of 
the MWfl-2 projection 
I lie tore tube, a video 
stage capable of a greater 
output voltage than that 
obtainable with EF80 
may be desirable. A 
suitable circuit using 
l'L83 is shown in Fig. 7. 
An EF80 video stage is 
in practice seldom used 
in projection models. 

The cut-off limits fof 
the MW6-2 tubo are -40 

and —90 V. In ordor to cope with the highest cut-off value, the 
required peak-to-peak signal, assuming 30 per cent synchronising 
ratio, will bo 129 V. To allow for all tolerances, a nominal 
output of 150 V has been assumed in the circuit calculation. 

Frame Time-base Generator 

The frame-deflection coils require approximately 500 mA 
pcak-to-pcak for full deflection, and have a resistance of 12-2 ohms. 



-VltiKo UtrTi'UT 81461 Urjt.v; I'l.s:;. 




FIU. E.— FUASIH TMK-UASK liKXKLU'roll UHCUIT. 



84 



TELEVISION ENGINEERS' POCKET BOOK 



f p- TOJWIWJ_C 

. llN PROTECTIVE 

J Q-i^L I I IWF 




Wta, 0.— Line Time-bask Generator Circuit 

A suitable circuit for framo scanning, using an ECL.80 triode- 
pentode, a silicon-iron-cored blocking oscillator transformer and 
a 23*5 : 1 output transformer, is shown in Fig. 8. 

The circuit has ample reserve of scan, and draws a total 
current of 13 raA only from the 350- V H.T. line. 

Indications of the currents and potentials appearing in the 
circuit are also givon in Fig. 8. 

Line Time-base Generator 

Tlie line-deflection coils roquiro 825 mA peak-to-peak to scan 
fully, and have an inductance of 3-24 mil. 

A projection receiver employing the Mullard 25-kV E.H.T. 
unit normally has a 350-V H.f. line available for the line time- 
base, and there is therefore little advantage in employing an 
energy -recovery system. 

A suitable circuit employing the triode section of an ECL80 as 
blocking oscillator and a FL81 as output valvo is shown in 
Fig. 9. 

Protective Circuits 

If either of the time-base units should become inoperative, 
the high-velocity electron would destroy the screen surface 
along a line which would be horizontal or vertical according to 
which time-base was out of action. Means must therefore be 
provided to cut off the beam in the event of the failure of either 
or both the time-base units. A circuit possessing all the necessary 
characteristics would be very complex, and it is therefore neces- 
sary to make some compromise. The circuit shown in Fig. 10 
has the advantage of simplicity and also has the essential charac- 
teristics. 



PROJECTION TELEVISION 



85 




10.— PROTECTIVE ClJKTlT IS CONJUNCTION 
WITH AS KFSO VlllJCU OLTH"r ST AUK. 



The voltage appear- 
ing at the anode of the 
frame - output valve 
(Point A in Fig. 8) is 
taken via a capacitor- 
resistor coupling to 
one diode anode (V6A) 
of the double diode 
V6, type EB91. A 
potential of approxi- 
mately 90 V positive to 
the chassis is obtained 
across resistor R35. 

The end of the 
line-deflection coils at 
which the flyback 
pulse is positive-going 

(Point B in Fig. 9) is connected via a limiting resistor R32 to the 
second anode (V6B) of V6, and a steady potential of at least 150 V 
is produced across resistors R33 and R34. R33 is the brightness 
control, and its slider is connected to the picture-tube grid via 
resistor R36. This sets the grid of the picture tube over a range 
of potentials suitable for a brightness control when the cathode 
of the picture tube is taken to the anode of tho video valve as 
shown in Fig. 6. 

If the frame circuit fails, tho potential at all points on tho 
chain R33 and R34 falls by 90 V— sufficient to cut off the picture 
tube. Similarly, if the line circuit fails, the total voltage across 
H33, R34 and R35 falls by 150 V, and the proportional change at 
the grid of the picture tube is again sufficient to cut off the tube. 

This circuit is suit- 
able for use in the 
video stage employing 
an EF80. It does not, 
however, provide ade- 
quate protection with 
a video stage employ- 
ing a PL83. This is 
ilue to the lower mean 
anode potential of 
the PL83, and also 
to the greater video- 
drive voltage applied 
to the cathode - ray 
tube. For this reason 
the circuit shown in 
Fig. 11 has been de- 
vised. 

In this circuit the end 
of the line-deflector Fl0 _ n.— protective Oirclit in conjunction 
coils at which the with a PWS Video Output stage. 




Line 

Dctlictc 

Colli 



Control grid of 
1 •'Ptcluri fub< 



86 



TELEVISION ENGINEERS' POCKET BOOK 



flyback pulse is positive-going is connected to the anode of the 
diode VIA via a limiting resistor Kl and coupling components 
CI and 115. The positive, rectified output from the diode 
cathode is utilised by the brightness control R6, which supplies 
the grid potential of the picture tube. Thus, a failure of the 
line time-base biases the picture tube beyond cut-off. The 
coupling components CI and R5 are included to ensure that a 
waveform with a mean component negative to earth appears at 
the anode of the diode VIA. This mean potential is applied, via 
the smoothing components K2. K4 and C4, to the suppressor 
grid of the video valve. In the absence of any other applied 
potential, the anode current of the video valve is then cut off 
and the picture tube, having its cathode connected directly to 
the anode of the video valve, receives no signal and assumes the 
positive potential corresponding to that of the H.T. supply. 
The beam is therefore cut off. 

Under normal working conditions, however, a positive potential 
derived from the frame time-base circuit via the coupling com- 
ponents C3 and R3 and the diode V1B restores the suppressor 
grid of the video valve to approximately cathode potent iaL 
If the potential derived from the frame time-base is established 
before that derived from the line time-base there will be a 
tendency for the suppressor grid of tho video valve to go positive, 
thereby causing secondary emission, which, in turn, will cause 




FIG. IS (a).— KAMA' MCLLAIU) E.TJ.T. T/MT FOR VKOJECTTON RECKIVERS. 

This unit provides a regulated supply at 25 kV by means of the triodc section of an 
EBC33 1,000-c/s blocking oscillator driving BO KL38 amplifier which produces anode 
pulses La the order of 8-9 kV : a vollage-tripler circuit using three KY51 rectifiers 
uroduces the full E.TT.T. Voltages across the additional Winding on the " ringing " 
transformer are rectified by the diode sections of the BBCM and fed to the grid of 
lie KL31S lor automatic voltage regulation, which is affective with our nuts "un to 

!>fiO/l,\. " ' 



PROJECTION TELEVISION 



87 



the suppressor grid to become more positive until " blocking " 
occurs. A third diode V2A is included to eliminato this risk. 

From tho foregoing description it is seen that when both 
time-bases are operating the picture tube is correctly biased and 







Mt4J 




* 25 
o 



H e 



i I* 




I 



fed with signal. If the frame time-base fails the picture tube is 
cut-off by its cathode going positive, and if the line time-base 
fails the picture tubo is cut off by its grid going negative. 

This circuit relies for its operation on a comparatively largo 



TELEVISION ENGINEERS' POCKET BOOK 



88 

change in the anodo potential of the PL83, which occurs between 
the quiescent and cut-off conditions, and is unsuitable for use 
with a video stage employing an EF80, in which the change of 
anodo potential is not sufficient to provide adequate tube cut-off. 

H.T. Power Supply Unit 

The requirements of the E.H.T. unit in large measure deter- 
mine the design of the H.T. power -supply unit in a projection 
television receiver, 

Tho E.H.T. unit must be supplied at 350 V from a source 
having a resistance of between 250 and 550 ohms. It will draw 
from 25 to 55 m.4, according to the picture content. 

A 350-VI H.T. line is often provided by means of an overwinding 
on the mains transformer. 

Typical E.H.T. circuits are shown in Figs. 12 (a) and 12 (b). 

ADJUSTMENTS 
Projection Television Focusing 

In a direct-viewing television receiver focusing is a matter 
of adjusting the current through the focusing coil or, in the case of 
permanent-magnet focusing, adjusting the permanent magnet 
on the neck of the tube. In projection television, however, in 
addition to accurate focusing of the picture on the face of the 
cathode-ray tube, it is necessary to adjust the position of the 




PROJECTION TELEVISION 



89 






Fig. 13.— Adjustments for Mechanical Focuanra. 



. 



face of the tube with respect to the spherical mirror to ensure 
that the pictures is accurately focused on the viewing screen. 
Focusing a projection television receiver is also a simple opera- 
tion, provided it is tackled in the right way. It should pre- 
ferably bo carried out while a test pattern is being transmitted. 
It can, however, be done when no signal is available, the image 
then consisting only of the scanning lines. 

If the picture is hopelessly out of focus the normal electrical 
focus control must first bo "adjusted, but if it is found that a 
strip of picture is already in correct focus, only the mechanical 
adjustment described below need be made. 

Note that these instructions, and Fig. 14, refer to a picture 
which emerges from the corrector lens with the scanning linns 

Pm. 1 (. sroKr^ivr Stacks in MRQBASKU& 

FOCUSISii. 
The shaded area represents strip of picture in fori is. A 

parallel to the axis of the tube. In some 
receivers the lines may be at some other 
angle. This will result in the strip of 
picture which is in focus being at a 
different angle from that shown in 
Fig. 14, but does not affect the method of 
adjustment. B 

(«) Remove the red locking plate from 
tho front of the optical unit by with- 
drawing four screws, see Fig. 13. 

(b) Slacken the knurled lock-nuts of 
screws 61, 62 and 63. 

(c) Turn screw 61 to one extremity 
of its travel. This results in a narrow 
strip of picture only being in focus (see C 
" A ", Fig. 14) if the raster is correctly 
focused on the face of the cathode-ray 
tube. If a strip of picture is already 
in correct focus on the viewing screen, operation (c) may not 
be necessary. 

(<l) Turn screws 62 and 63 simultaneously in the same direction 
until tho strip of picture which is in focus passes through the 
exact centre of the picture (soe " B "). 

(e) Turn screws 62 and 63 in opposite directions until the strip 
of picture which is in foeus is both central and vertical {see " C "). 

{/) Adjust screw 61 until the strip of picture which is in focus 
widens and ultimately covers the wholo picture area, and adjust 
for best results. 

(ff) Tighten tho knurled lock-nuts of screws 61, 62 and 63. 

{h) Do not replace the red locking plate, as this may throw the 
focus out of adjustment. The locking plate with its four screws 
should, however, be preserved for use if the receiver has to be 
sent away for service. 




90 



TELEVISION ENGINEERS' POCKET BOOK 



Centring Picture on Tube Face 

The face of the picture tube should be viewed through the 
corrector plate. Slacken off the focus-coil locking-screw, which 
is sometimes painted rod and is situated very near to the picture- 
tube retaining clip. Adjust the two hexagonal -headed bolts on 
the Mange of the focus coil until the picture is exactly central 
on the tube face. Tighten the focus-coil locking-screw, taking 
care not. to alter tho position of the focus coil. 

Picture Centring on Screen 

If the picture is not central on the screen (but is central on 
the tube face) slacken the two wing -nuts locking tho optical unit 
levelling screws. Adjust tho screws appropriately: the left- 
hand screw moves the picture vertically, and the right-hand one 
moves the picture horizontally. 

Cleaning Projection Mirrors 

Occasional cleaning of the front alominised mirror of projec- 
tion television receivers may bo necessary in order to obtain a 
clear picture. Tho treatment to be adopted largely depends 
upon the stato of the mirror, but the following methods have 
been suggested by Mullard, Ltd. 

(1) If the dust is loose, the mirror should bo carefully brushed 
with a very soft brush. 

(2) If the surface of the mirror is at all cloudy, the surface 
should bo washed with a detergent such as Lissapol solution, 
and afterwards rinsed with ilislilleil water, preferably allowing 
tho surplus liquid to drain off. Only soft cotton-woof should bo 
used to apply tho detergent solution, and for removing the surplus 
liquid, should time not permit draining. 

(3) If the surface is greasy, then it may be necessary to use a 
solvent such as benzene, finally drying with best-quality soft 
cot ton -wool. 

Projection E.H.T. Dangers 

The 25-kV electron beam of projection models produces soft 
X-rays, which are normally shielded from the operator by the 
optical box, Should it be necessary to operate the cathode-ray 
tube outside of the optical box, it is recommended that a lead- 
glass shield be used. The equivalent lead thickness of the shield 
should not bo less than 0-5 nun. 

This article has been compiled largely from information 
supplied by Mullard, Ltd., on their projection television 
system as used in a number of wt.s made by various 
manufacturers. 









[SECTION 7] 

BAND in CONVERSIONS 

Ai.i. domestic television receivers produced to-day are fitted 
with tuning arrangements which allow the viewer to select any of 
the Channels in Band I or III. 

A fair number of older receivers in daily use, however, are 
limited to the reception of Band I channels and, in some cases, 
to the reception of a single channel only. 

These receivers fall into two categories, superheterodyne and 
T.H.F. The superhet receiver, generally, will tune to any one 
of the five Band I channels. Tho intermediate frequency used 
will vary according to tho manufacturer, see list on page 19',). 
T.R.F. receivers will receivo only one channel in Band I. 

It is to these older receivers that conversion mothods must bo 
applied. 

Some receiver manufacturers have mado available converters 
for certain of their models. No difficulty should bo encountered 
in fitting these, as provision will, generally, have been made in 
the receiver to allow this converter to bo readily installed. 

As with receivers, so converters fall into two categories: (i) 
'" Aerial to I.F." converters; and (ii) " Band III to Band 1 " 
converters, often referred to as " Universal " converters. Both 
typos have thoir particular application, but where a choieo 
between (lie types may bo mado tho "Aerial to I.F." type of 
converter is strongly to be recommended. The reasons will 
become apparent later. 



CONVERSION OF T.R.F. RECEIVERS 

Tho number of T.R.F. receivers likely to require conversion 
is probably small; but when one is encountered certain problems 
may arise of which it is as well to be forewarned. 

The type of converter required for this application is the 
"Band III to Band I"; these are readily available in both 
assembled and kit form. 

The unit functions as follows. Band I and Band III signals 
are supplied to the unit from tho respective dipoles by moans 
of separate co-axial cables, sockets being provided on tho unit 
as a means of connection. A switch is provided so that t lie user 
may seleet his Band I or Band III programme. Whon the 
normal Band I programme is selected thu Band I signal from 
tho aerial is switched through to the converter output socket , 
whence it is connected by eo-n^ial cable to tho aerial input 

Si 



92 



TELEVISION ENGINEERS' POCKET BOOK 



H 



T.R.F OB 5UPERHET RECEIVE*) 



\ socket; 



+0 



(«) 



H 



»' 



SUPERMET RECEIVER 



f- w — r^p~ ^ — 0~ C T\ J 

! SAMD I FRONT-END 



(b) 



NOT USED 
r C MAY BE 
CONVERTED 
TO EXTRA 
IF. STACE 



Fin. i.- the two Basic masons o» conversion: (a) .band he to hash t, in 
which do converter Oomvwxs the tund hi signals to tub hand i 

FREQUENCY OK THK ItECKIVER, l-'KKIJtMi INTO THE RECEIVER AERIAL SOCKET; 

(l>) akrialto l.F.. in Which the Converter Contorts the hand ill signals 

T(l THE RECEIVER F.F., KEPI.ACINC, THE RECEIVER li.I''. AND F,0. STAUES. 

terminals of the receiver, which then functions in the same 
manner as heforo conversion, as the signal will not have been 
affected by its passage through the converter. 

When the alternative programme in Band III is selected the 
Band I signal is disconnected from the receiver. The Band in 
signal is applied, via a timed matching transformer, and usually 
an R.F. amplifier stage, to the grid circuit of a valve acting as a 
signal mixer; this valve mixes the Band III signals with the 
output from a local oscillator, which is often in one envelope 
with the mixer section or may be of the self-mixing type. The 
local oscillator frequency is adjusted so that when heterodyned 
with the Band III signal input a difference frequency similar to 
the Band I frequency in use in the television receiver is produced 
at the anode of the mixer valve. The anode circuit is tuned to 
Hi is frequency and a further matching transformer passes tho 
convertod signal to the output sockets of the converter. 

This signal will now be handled normally by the receiver, but, 
of course, the programme material will be that of tho Band II I 
transmission. 

Power Supplies 

Converters of the type under discussion are usually marketed 
as units with their own power supplies. If it is decided to instal 



BAND 



CONVERSIONS 



93 



,i unit to draw it* power from tho television receiver the following 
points should be noted: 

(a) Tho receiver power supply must be capable of supply- 
ing tho extra load, 

(6) If the receiver has, as usual, a mains connected chassis, 
then the converter chassis will also be mains connected. 
This is a dangerous arrangement unless tho converter is 
specifically insulated for such usage. 

(c) The valves used in the converter must have heaters of 
voltage and current rating suitable for inclusion in the 
heater chain of the receiver. 



Upper Sideband Receivers 

A pitfall peculiar to Channel 1 (London) may be encountered 
when converting the older T.R.F. receiver. This is as follows: 

It was not uncommon for the input circuit of the receiver to 
be designed to accept the full double sideband response of the old 
Alexandra Palace transmitter. Thereafter the sound signal was 
taken off and amplified in the sound R.F. strip, the vision signal 
f hon being passed to tho vision U.K. stages, which were aligned to 
accept the upper sideband only. Tho advantage of this arrange- 
ment was that good sound rejection on vision could bo achieved 
without sound traps. 

This type of receiver will not accept lower sideband trans- 
missions* without serious degradation of tho picture. As all 



BAND m 
DIPOLE 



OSCILLATOR 




ANT1- , 

PATTERNING 

UNIT 



FIG. 2.— SSllOWISO THE BASI) IfW SWIXtitUKS OF A CONVERTER WITH 
" ANTI-I'ATTERNIXG " UNIT ADDED. 



94 



TELEVISION ENGINEERS' POCKET BOOK 




IE OUTPUT 
BAND-PASS _w(FOR METHODS 

TUNED CIRCUIT ■" OF COUPLING 

SEE TEXT) 

VIQ. 3.— UliOCK SCHEMATIC DIAGRAM UK AX " AiilUAI. TO T.F." TSANI) III COKVEHTER. 
" U.MVKHSAL '* UO.WKHTKRS l/SK TitK SAMK lUSIU AUUAXGKUEXT. 

stations now radiate single-sideband transmissions this type of 
receiver is not really amenable to conversion. It may be possible 
to re-align the receiver to accept more of the lower sideband, 
but, if this were done, the probability is that rejection of sound 
on vision would be poor, and it would become necessary* to insert 
sound-rejector coils. 

Patterning 

Although it is necessary to use the above type of " Universal " 
eon verier for T.R.F. receivers, they hove inherent disadvantages 
which tuuke them unpopular for gonoral use. The iirst is that 
when the receiver is accepting a signal from the converter, con- 
i.-iiniim Hand ill programme material, ii will also accept a Haml 
I signal introduced by a lead or by direct pick up. In this case 
the two programmes are seen superimposed one upon the other, 
and this in bad cuses makes viewing impossible. In the leas 
serious cases a background pattern will be observed. 

When the receiver is accepting a Band I signal from the con- 
verter the Band III signal and the conversion action are switched 
out; the Band I picture therefore is " clean ". Any lead or 
direct pick-up of Band III signal is not accepted by the re- 
ceiver. 

Secondly, the converted Band III output from the unit, since 
it is at the frequency of the local Band I station, is a potential 
source of interference to neighbouring receivers on the Band I 
c h a nn el , particularly after it has been amplified in the main 
receiver. The signal may be radiated in several ways, from the 
eo-axial cable connecting the converter to the receiver, from i hi- 
R.F, circuits of the receiver itself or by inductive or oapacilivt- 
coupling, within the converter, to the "aerial input circuits and 
thence to the dipoles. 

This latter typo of radiation condition is much reduced if an 
R.F. stage is incorporated in the converter circuitry, as it acts as 
a buffer between the mixer grid circuit and the aerial. 

A unit has been marketed which is designed to remove the 
Band I " break-through " when viewing a Band III pioture. 



BAND 



CONVERSIONS 



95 



This is achieved by introducing a sample of Band I signal to the 
required signal such that it is 180° out of phaso with the Band 1 
interference and thus cancels it out. Controls are provided to 
nnable adjustment of the phase and amplitude of the correction 
signal. 

This unit, howovor, does not reduce interfering radiation from 
tho installation into neighbouring receivers. 



CONVERSION OF SUPERHETERODYNE RECEIVERS 

Many thousands of this type of conversion havo been success- 
fully carried out, with complete satisfaction to the user, since the 
start of alternative programme broadcasting. 

Converters for superheterodyne receivers should bo of the 
" Aerial to I.F." type if the most satisfactory performance is to 
ho attained. The majority of these incorporate a twelve- or 
thirteen -channel switch so that programme selection is simple 
and facility is available for the reception of further channols in 
Hands I and III if required, should the user move to a district, 
served by different channels. These tuners are similar in design 
hi those used in multi-band receivers. Attached to the converter 
are generally two leads up to several feot in length to provide the 
method of connection of tho converter to tho receiver. Pre-set 
gain controls, one each for Bands I and III, aro provided so that 
similar intensity pictures may be obtained without resorting to 
adjustment of the receiver. 

The method of installation and coupling of tho T.F. signal to 
1ho receiver varies according to tho manufacturer, two methods 
of coupling being shown in Fig. 4. 

In most cases the installation is carried out as follows. Tho 
R.F. amplifier and mixer valve of the receiver are removed and 
n -placed with the plugs provided on the extonded leads from the 
converter. Power is taken from tho R.F. valvo socket, the I.P. 
output from the converter being injected into the mixer valvo 
socket. 

Thus tho normal R.F. tuning or the receiver has been replaced 
by that of tho converter with tho facility to select any channel, 
i he I.F. amplifiers of tho reeoiver remaining unchanged. The 
receiver may now, in fact, compare very favourably in perfor- 
mance and facilities with much later models. 

Means are generally provided to soeure tho converter inside 
the receiver cabinet so that tho only external projection is that 
of the station selector knob. Some converters ore offered with 
a small case which permits tho unit to stand external to the 
receiver, the two leads to the receiver being arranged in the most 
suitable way. Remarks on safety precautions apply here also. 
«nd care should bo exercised to ensure that the converter manu- 
facturers' instructions on installing are closely followed to ensure 
that no " live " parts of the equipment aro available external to 
tho receiver cabinet. 



96 



TELEVISION ENGINEERS' POCKET BOOK 



BAND III CONVERSIONS 



97 




CONVERTER 
MIXER 



Fl<i. 4. 



AliTKItKATIVE MKTMntiS OF « 'nrrl.INi; 
0OMVBB39B TO HKCK1VKII. 



AKIUAI, TO I.F. 



(a) Coupling to the grid of the mixer. The low gain of this arrangement is com- 
pensated by the fact that the receiver mixer acts as an I.F. amplifier. Jt2 in a low 
value terminating resistor. 

(6) Capacity coupling to mixer anode. Because of the high impedance of tiiis 
muplinff, the gain is such that it is unnecessary for the receiver mixer to act as Ml 
l.F. amplifier. 

Converter Specification 

A great number of design differences exist between the receivers 
which are normally presented for conversion, and a number of 
these require to be known before a converter of the correct 
specification can be obtained. 

The information required is as follows: 

(a) type of valve heaters in use, i.e., series or parallel 
wired. If in series, then the current rating will be required; 
if in parallel, then the voltage rating will be required; 

(6) the intermediate frequency of the television receiver; 






(c) whether the oscillator of the receiver, before conver- 
sion, is higher or lower than the signal frequency: 

(rf) in the case of tuners with clip-in coils it will be neces- 
sary to specify the channels it is required to receive. 

In many cases the converter manufacturer will recommend 
his product for specific receivers, in which case the above informa- 
tion need not be known, and quotation of the converter catalogue 
number is sufficient. A number of receivers, particularly fringe - 
area models, were fitted with two R.F. stages preceding the 
mixer. In order to carry out a conversion one method is to 
remove only the two R.Fl amplifier valves, leaving the mixer in 
ttitii. The converter power lead is then plugged into one of the 

H^led valve-holders. The converter I.F. output is coupled 
into the grid of the mixer valve, which then assumes the role 
of an I.F. amplifier. The oscillator of the receiver is then 
prevented from functioning, possibly by removing its H.T. supply. 

By using the converter in this fashion the overall gain of the 
receiver is maintained and power taken from the receiver is 
more nearly that normally supplied. 

Conversion Problems 

Tho position of the converter heaters in the heater chain of a 
universal-mains type of roceiver may require consideration. 
Some receivers have their K. F. and mixer valves relatively 
■■ lutih up ,: I he heater chain, that is to sa\ away from the ground. 
This may give rise to modulation hum troubles on some conver- 
sions, and the cure is to rewire the converter heaters (plugged 
mio U.K. amplifier and mixer valve-holders) " down " the chain, 
nearer to chassis. 

Another fault, commonly encountered bat mystifying on first 
acquaintance, is as follows: A picture is obtained, after conver- 
sion, but no sound can be obtained; tuning the converter 
oscillator control will bring in the sound but cause tho picture to 
disappear. Tho trouble is that an incorrect type of converter 
has been obtained. The receiver oscillator has, for example. 
been working on the low side of signal frequency, whereas the 
oscillator in the converter is working on the high side of signal 
frequency. Or, conversely, the roceiver oscillator may have 
been on tho high side and the converter on the low. 

Reference to Fig. 5 will help to clarify this point. If the I.F. 
response " A " is considered to be that of a converter coupling 
circuit and the response " B " that of a receiver I.F. amplifier: 
also the converter is considered to have its oscillator frequency 
higher than signal frequency, and the receiver, before conversion, 
had its oscillator below signal frequency; then, by timiiiL' the 
converter oseillator, response " A " can be made, to move through 
response " B '*. If, now, the two sound carriers are set one upon 
'he other a sound signal will be heard, but it will bo obsorved 
that the vision signal-carrier frequencies do not correspond and, 

1> 



98 



TELEVISION ENGINEERS' POCKET BOOK 




OSCILLATOR HIGHER 
THAN SIGNAL FREQUENCY 



OSCILLATOR LOWER 
THAN SIGNAL FREQUENCY 



Fic. 5.— Idealised i,f, itKsrossics with Oscillator Wuhkim, iin;:si:h and 
Lowkh than SlQKAX PEtaqOBHOT. 

therefore, no picture will result. Again, if the vision-carriers 
are superimposed by this means and a picture obtained, then 
the sound-carrier frequencies do not coincide and no sound signal 
is heard. 

When the installation is complete it is good practice to make 
voltage and current measurements in the section of the receiver 
affected by the conversion. A few simple calculations will 
quickly indieato whether abnormal conditions exist in tho 
receiver, and, should this be so, these conditions should be 
" i-learod " before the conversion is considered complete. 

U.H.F. Reception 

Techniques for reception on Wands IV and V differ in several 
respects from those used on Bands I and III. " Coils " aro often 
replaced by tuned lines, which may be in the form of co-axial 
trough-lino elements, while even when retained the coil may 
comprise little more thiiti a hairpin of stout wire, t'aseode r.i*. 
amplifiers are not suitable for Band V and the r.i'. stage, whero 
lilted, is usually of the grounded -grid type; it is quite common 
however to omit this stage altogether. .Silicon crystal diodes 
are generally used as mixers. Oscillator stability is a problem 
and two solutions are possible; one is to include voltage regula- 
tion as well as temperature compensation; tho other is to run 
the oscillator on a much lower frequency and to include a har- 
monic generator (which may simply he a crystal diode) between 
the oscillator and the mixer. 






[SECTION 8] 

INSTALLING AND SERVICING RECEIVERS 

INTRODUCTION TO FIELD SERVICING 

by E. C. Howell, M.Brit.I.R.E., A.I.E.E. 

Television installation and servicing work demands qualifica- 
tions of a type different from those normally associated with 
engineering, or with work carried out in tho workshop under 
the direct supervision of senior staff. The television servicing 
engineer is brought into close association with the general 
public to a far greater extent than his radio colleague; this is 
partly because the modern television receiver is not an easy 
instrument to transport by van, and partly because owners 
are loath to part with their receivers if they feel that it is at all 
possible for repairs to bo carried out on the spot. For these 
reasons, the service ongineer — if he is to improve tho prestige 
of his firm and his occupation — is called upon to combine the 
qualities of a first-class technician with those- of a sales manager : 
as essential as knowledge of television technique is a good 
working knowledge of human psychology. 

If such requirements appear to bo setting a high standard, 
then it. is rightly so. for to meet the rapidly expanding demand, 
there is unlimited opportunity for men of tho right calibre who 
are capable of handling people as well as expensive nud intricate 
test equipment, and who seek work that provides a constant 
variety of surroundings coupled with ever-changing technical 
problems. 

It is tho purpose of this introduction to underline tho personal 
rather than the technical problems, which are dealt with else- 
where in this book. 

Obviously it is a prime requisite that the engineer must have a 
first-class knowledge of the apparatus that he is called upon to 
repair; detailed knowledge of the finer points of a particular 
design comes only from constant handling of similar types of 
equipment. New models and new circuits are constantly being 
introduced which require referenco to technical literature and 
circuit diagrams, but, it is bad psychology to pore over technical 
data too long in the presence of the customer, who may be only 
too ready to suspect that this means tho engineer " does not 
know his job ". When called in to service a model that is 
unfamiliar try, wherever possible, to study all available litera- 
ture beforehand. 

fl!> 



100 TELEVISION ENGINEERS' POCKET BOOK 

Tact 

The field engineer must bo prepared to learn something from 
the proven technique of sales personnel : ho must bo well spoken, 
polite, tidy, tactful and above all must not become annoyed 
with a difficult customer. Not only is confidence created, but 
attention to such points will make 'for a better atmosphorc in 
which to work. It is of little use being a "genius in dirty 
(l;it i in -Is " when calling on a house-proud housewife ; nor will she 
bo pleased if wrappings and other bits of paper are left for her 
to clear up, and her carpets littered with cigaretto ash and bits 
of wire. Remember also that first appearances count for much, 
and dirty shoes and open collars seldom inspire confidence. 

Tactfulness is difficult to define but worthy of cultivation if 
not already possessed as a gift. From a service engineer's 
viewpoint, it consists largely of " saying nothing at the right 
moment ". If he has received wrong instructions from his office, 
or some misunderstanding has occurred, ho should be careful 
not to run down his firm to the customer. He must offer to 
" look into the matter at once ", and then diligently do so. 
Never belittle the customer's set, even if it is a little outdated or 
poorly constructed. Owners are extremely sensitive to such 
criticism, which does, after all, tend to reflect on their original 
choice of the set ; explain, if necessary, that now improvements 
have been made recently and are incorporated in the latest 
models. 

Generally, it is not the field engineer's job to discuss charges, 
and lie should be most wary in exceeding his authority by 
suggesting a " possible price , Similarly, he should not make 
any promises to customers without obtaining authorisation 
from his office; but promises and appointments, once made, 
must on all accounts be kept. Should it be impossible to keep 
an appointment, the customer must be advised and not left 
waiting for an engineer who never arrives. 

Records 

Care must also be taken in entering up " job cards ". Abbre- 
viated remarks such as " F.O.T. rep. N.U.G., etc." may be 
satisfactory if they are part of a definite code recognised by the 
oince staff, but if not are liable to load to wrong charges, and to 
loss of confidence by the customer, who generally has a fair idea 
of what has been done. 

Remember that the engineer represents his company, and 
the loss of customers due to carelessness or faulty work not only 
affects the livelihood of the engineer concerned but also that of 
all other persons employed by his company. On the other hand, 
a fully satisfied customer reflects ultimately on the standing of 
all concerned; and leads to tho advancement of the service 
engineer. 

E, C. H. 



INSTALLING AND SERVICING 



INSTALLATION 



101 






The first point to be considered is the best position in the room 
where a receiver is to be installed. If possible, the screen should 
be situated so that light docs not fall directly on to it. It is 
advisable to provide a low-wattage lamp, as viewing in a com- 
pletely darkened room causes eye-strain. Tho mains lead 
and aerial down- lead feeder should be placed whero they are not 
likely to be damaged in any way, and the latter should be kept 
as short as possible. 

Tho mains supply socket must be rated at least 2 A, and a 
television receiver must always be adjusted to suit the supply. 
The frequency of A.C. mains supplies should be determined, and 
i he correct rating of the mains supply fuses is another important 
• nnsideration. A step-up auto -transformer may be used where 
tho A.C. mains supply is of lower voltage than that for which tho 
receiver is intended. A.C./D.C. receivers will operate from D.C. 
supplies only when the plug is inserted into the supply socket tho 
correct way round. 

Karth leads should be of heavy gauge wire, and must be kepi 
fis short as possible. A copper earth tube or plate, with a large 
surface area and going deep into damp ground, is best. A main 
cold-water supply pipo may be used, but gas, hot-water or 
telephone installations must on no account bo used. Most 
television receiver chassis arc at mains potential, and direct 
connection to tho chassis should never be made. 

ADJUSTING CONTROLS 
Tho controls provided in a modern television roceiver fall 
loughb into three categories: the main user controls, mounted 
ai I he front, side or top of the receiver; auxiliary controls, such 
as those for ihe tone-bases, which are pro-set but which can 
tfcnerallv he readilv tid justed eiilmr by I lie user or by the engineer ; 
and finally, those which can be adjusted onlj with the protective 

cover removed and which may require tin- changing of soldered 
banpingB, etc. Willi Ihe development of circuits which lire less 
subject to variation with changes in mains voltages, Ageing oi 
valves, etc., there is a tendency for ibis third category to increase : 

fur example, focusing, width and line linearity are now often 
intended for adjustment only by the engineer. 

Time-base Controls 

Tho controls usually found are the line and frame hold, the 
line ami liana' linearity (sometimes called line and frame form), 
the width (sometimes "called line-amplitude) and height (some- 
times called frame-amplitude) controls. In many receivers two 
frame-linearity controls arc provided, one affecting tho top oi 
the picture only, 

The correct procedure is first to adjust the frame- and line- 
hold controls to give a steady raster — a picture that tends to 



102 



TELEVISION ENGINEERS* POCKET BOOK 



break into vertical sterna or to move up or down indicates ilnn 
an adjustment of one of the hold controls is necessary. Roughly 
centre the picture by the centring magnets on tube neck. Nex1 
adjust the width and height controls so that the picture just fills 
i In- screen. Then ndjust the linearity controls to compensate 
for auj- irregularities, such as cramping, in tho picture. Where 
two frame-linearity controls are provided, the ono affecting tho 
top o(" tho picture only should bo adjusted first, the overall 
control being adjusted last. It is sometimes desirable, in order 
to achieve good linearity, to adjust the height and width controls 
so as to overscan the tube face when making adjustments to the 
linearity controls. After adjust incuts to the I ime-basc amplitude 
and linearity controls it will often be necessary to re-centre the 
picture. 

In some models which include flywheel line synchronisation, 
a switch is incorporated in the line hold control, and in such oases 
the knob of the control must be depressed before it can be 
rotated. Preset line hold controls are also common on such 
models. The usual practice in adjusting these is to set the main 
hold control to mid -travel, short out (he line sync, pulses (in 
some eases it may be easier lo remove both the frame and line 
syne, pulses], and adjust i he pie-set control so thai the picture 

is synchronised (or slowly running through if the frame sync, 
pulses have been removed*. The width and lino linearitj 
controls may need slight readjustment afterwards. In some 
models provision is made to short -circuit completely the By wheel 
eiretiit when the set is used in an area of good signal strength; 
this makes the setting of the line hold control less critical. 

In most modern receivers the line linearity control takes ihe 
form of a shorted-turn loop, which is filter! beneath the deflection 
coils, around the neck of the picture tube. This device may also 
be used to control the width. Further information on this type 
of control is given in the basic circuitry section. 

Interference and Sensitivity Controls 

Two other pre -set controls usually found are tho vision- 
interference limiter and tho sensitivity control. 

The vision- interference control may take the form of u (ire-set 
potentiometer or a plug and socket" adjustable in a number of 
fixed steps. .Most forms of limiter, when set to give maximum 
clipping, will cause some flattening of the highlights of the 
picture. Vision-interference limiters should therefore always be 
adjusted to the minimum clipping posiiion consistent ' wit h 
sat isluetory reeepi ion. 

A sound- interference limiter adjustment is provided in a 
number of sets: as with vision interference limiters, the adjust- 
ment should be set to give the minimum limiting action consistent 
rt h!i freedom from interference. 

The sensitivity control is fitted to vary the gain of the receiver 
so that it may be adjusted to suit the signal strength of the area 



INSTALLING AND SERVICING 



103 



in which it is installed. If the signal strength is loo great, 
sound-on-vision and vision-on-sound interference may bo caused, 
and the sensitivity control will in such conditions need to be 
reduced so that tho interference is eliminated. 

Miscellaneous Pre-set Controls 

Other pre-set controls commonly fitted arc for picture quality, 
line anti-striation and line drivo adjustmont. The picture- 
(|iiality control usually takes tho form of a compression trimmer 
i r other arrangement for increasing or decreasing the capacitance 
in tho cathode circuit of the video output valve. This control 
should bo adjusted to give a sharp picture, free from smear, a 
compromise in some locations having to be sought between 
Hands I and III transmissions. 

Line anti -striatum or balancing trimmers arc fitted on the 
deflection coils to balance tho stray capacitances in the coils. 
Tho adjustment of this is normally carried out in the factory, 
and should only need readjustment if new dellcetion coils arc 
fitted. Tho adjustment is for minimum wavincsa in tho line 
scanning. 

Lino drive controls usually consist of a trimmer controlling 
the drive to the line output valve, and should need no adjustment 
unless valves in the lino time-base aro changed. The usual 
method is to adjust the control so that the E.H.T. voltage is a 
given value, as specified by the manufacturers. If out of adjust- 
ment, a faint white line tuny appear near Urn centre of the screen. 
I >amage to tho lino out [nit valvo or transformer can bo caused 
if this adjustment is not correctly carried out. 

In fringe aroas it is advisable to adjust the pro-set controls for 
average signal-strength conditions, as in these areas a certain 
amount of fading is to bo oxpected, and unless some such 
allowance is mode they will require constant attention. 

Mechanical Picture Adjustments 

Around the nock of the picture tube arc situated tho deflection 
coils and also usually Bevoral magnets for such purposes as 
centring and focusing tho picture, and for reducing ion burn. 

The deflection coils aro housed close up against the bulb of the 
picture tube, and may be rotated, after loosening the clamping 
screws, so as to level or square the picture. Correction magnets 
may also be found fitted against the bulb of the tube to correct 
for barrel and pin-cushion distortion, etc., and to remove corner 
shadowing. Behind the deflection coils are situated magnets 
controlling the focusing (if magnotic focusing is employed) and 
centring of the picture. These are adjustable by means of suit- 
able levers or knobs. At tho rear of the picture-tube neck is 
frequently fitted an ion-trap magnet. The adjustment of this 
is dealt with below. 






104 



TELEVISION ENGINEERS* POCKET BOOK 



Adjusting Ion-trap Magnets 

Ion-trap magnets arc normally secured to the nock of the tube 
by means of a clamp, and to facilitate fitting there is usual Iv- 
an arrow stamped on the magnet, and a line along the neck of the 
tube. The magnet is normally fitted above the neck with the 
arrow pointing in the direction of the screen, but alternatively 
may be fitted with the magnot underneath and the arrow point- 
ing away from the screen. To fit and adjust the ion-trap magnet, 
the following procedure should be followed, preferably when a 
stationary test pattern is available. 

With all power switched off, and reservoir condonsors discharged 
if necessary, the magnot is pushed over the base of the tube 
with the arrow pointing towards the screen, and placed imme- 
diately over the lino marked on the tube nock. The catliode-ray 
tubo socket is then replaced, the receiver reconnected to the 
mains supply, ensuring that the chassis is not abovo earth poten- 
tial, and the brightness control .set to a position where the raster 
is just visible. To achieve this, it inny be necessary to adjust the 
position of the magnet slightly. . 

Then with the arrow over the line, the magnet is moved towards 
the screen until the focused raster is at its brightest. Tho 
brightness control is then re-adjusted until the peak-white 
portions of the imago are at a correct level, and, if necessary, the 
position of tho magnot adjusted slightly to obtain maximum 
brilliance. 

Where the picture cannot bo centred by adjusting tho position 
of tho focus field, the ion- trap magnet may have to be rotated 
slightly around tho neck; this operation, however, should not 
lead to any decrease in brilliance. 

When the picture fulfils the above requirements, lock the 
nctagnei in position by tightening the thumbscrew, ensuring that 
tho magnet, docs not change position while this is being done. 

Should it not be possible to obtain a position of maximum 
brilliance, it may be nocessary to substitute another magnet. 
The magnet should never he adjusted to remove a shadow if this 
involves reducing the brightness of tho picture ; this should bo 
done by adjusting the focus coil and /or deflection coils. 

Always handle an ion-trap magnet with care : it should not 
bo subjected to strong magnetic Molds or mechanical shocks. 
It should not bo allowed to como into contact with metallic 
objects. 

Steering Magnets 

Apart from picture correct ion magnets positioned close to the 
Hare el the tube and centring magnets a rou ml the neck of the tube, 
a steering magnet (sometimes known ns n "beam centring 
magnet ") in the form of a cirelin is often fitted around the neck 
of the tube for the purpose of ensuring that the electron beam is 
central within the onai aperture. 

Whether or not a steeling nmgnet is required is judged by the 



INSTALLING AND SERVICING 



105 



quality of the picture. A general smudginesa of "tails" on 

wliito spots may be an iiulieat ion of the need of a magnet, though 
these faults can bo caused by incorrect alignment of I ho receiver 
circuits. On some picture tubes where the steering magnet is 
not required it may nevertheless be fitted, usually at the extreme 
end of tho tube nock, where is has no influence on the electron 
l.ieam. The magnet should not bo discarded, ss it may be needed 
should tho tubo bo changed. In practice, the steering magnot 
is used for much the same purpose as the final adjustment of an 
ion-trnp magnet on a bent-gun tube, that is to say for general 
I lie tare quality rather than for brightness. The setting is de- 
termined by rotational and ax in I movement nlong the tube neck 
to a position which gives optimum freedom from blurring of 
lending edges. The adjustment should be carried out on Test 
Card "C" so that the resolution can be judged over the whole 
-crceri. 



User Controls 

The controls usually provided for operation by the owner are 
t he brightness, contrast, volume and, sometimes on older models, 
focus controls. The following procedure, which assumes that 
the pre-set controls arc correctly adjusted, may be followed 
when adjusting these controls: 

(1) Switch on the receiver fifteen minutes before the start of 
the programme, so that the receiver has time to warm up to 
normal working temperature. It is not, of course, nocessary to 
allow so much time ordinarily, but it is advisable when full 
■ idjustmont is being made. 

(2) When the tuning signal (see later) appears, turn the con- 
trast and brightness controls to minimum. 

(3) Increase the brightness slowly, until a very faint glow is 
just visible on the screen. Then reduce it very slightly until 
i he glow just disappears. 

(4) Increase the contrast until the topmost shapes on each 
side of tho circle in the tuning signal are white, and the shapes 
immediately below them are light grey. 

(5) Roadjust the brightness control so that the bottom shapes 
arc black and the shapes immediately above them ore dark 
Lirey. 

(6) Make a slight adjustment to tho contrast control to get the 
best contrast between the white and the light grey shapes. 

(7) Adjust the focus control, if fitted, to give the clearest 
definition to the vortical lines in the centre of the picture. 

The effects of the brightness and contrast controls on t he 
pictures are interdependent, and it is for this reason that the 
suceessive adjustments to them arc recommended. If the 
correct relative adjustment of these two controls is not found, tho 
brightness control will need readjusting whenever the overall 
brightness of tho scene changes. With a constantly changing 
scene, as is usual during the programmes, it is very difficult to 



106 



TELEVISION ENGINEERS' POCKET BOOK 



INSTALLING AND SERVICING 



107 




V\f\. ].— TRK n.B.C. TtlNISfl SIGNAL. 

(Cotcrtoiv B.lt.c.) 

arrive at the best relative settings Cur the brightness and contrail 
controls. 

A suggested method is first bo turn bolii controls to minimum. 
Increase the brightness slowly, until a very Taint glow in just. 
visible on the screen. Then reduce il very slightly until the 
glow just disappears. Increase tin- contrast to give whiles and 
light greys- Readjust the brightness for good blacks and dark 
greys. Finally, make a slight adjustment to the contrast oonl rol 
to obtain the best shade contrasts. 

Koine further adjustment of the picture may be neeessan 
whenever there is an appreciable change in ambient ligbting, for 
instance when a light is switched on or a curtain drawn. Nome 
receivers now fit an automatic contrast control using a light - 
dependeul resist or monnterl on the eabinel and connected in 
the A.G.C, line. 

The fine tuner emit rol should be adjusted for maximum sound 
consistent with good picl ure definition. An incorrect l\ adjusted 
control may cause sound-on-vision or vision -on -sound ami will 
degrade picture qua lit \ . 

B.B.C. Test Card « C " 

A speeial test pattern is included in the morning television 
transmissions on weekdays, and this has been designed to give 
an immediate indication of the performance of the whole trans- 
mitting and receiving chain. As the performance of the trans 







KB. 8. t:.r..r. TSES cum 
(fimirtaty li.a.t'.) 

milling equipment is maintained in accordance with the agreed 
standards during the normal periods of radial ion for test purposes, 
ibis Test Card '" C " can servo as a chock on propagation and the 
performance of the receiving apparatus. 

The eard, which bears the identification letter "("". incor- 
porates a number of pal terns, each designed to assoss one par- 
licular characteristic of the system, thus: 

Aspect Ratio.— Concentric black and white circles surrounding 
the five frequency gratings will appear truly circular when the 
width and height of the picture are adjusted to the standard 
aspect ratio of 4 : 3. 

Re^ol a Hon and Band-width - Within the circles there are two 
groups Of frequency gratings, each consisting of five gratings 
having black and white strips corresponding to fundamental 
frequencies of 1-0, 1*5, 2-0, 2;"> and It-0 Mc s. In the left -hand 
group the l-O-Mc/s grating is at the top, the frequency increasing 

towards the bottom, and in the right-hand group the order ifl 
reversed. The response of the whole system is required to bo 
uniform to 2-7 Mc s. so that the 2-6-Mc/a grating should be clearly 
reproduced, but the 8*Mc fi gratings may be blurred. The pic- 
lure must just fill the viewing aperture during the test, with the 
black-and-white border visible. 

Contrast. — A Jive-step contrast wedge appears in the centre 
of the test card. The top square is white, corresponding to 
100 per cent modulation, and the lowest square is black, oorreS- 



108 



TELEVISION ENGINEERS' POCKET BOOK 



ponding U> :{H per cunt modulation. The three intermediate 
squares should be reproduced as pale, middle and dark grey. 

Scanning Linearity. — -The background oi' the teat card is a 
middle grey, bearing a graticule of white lines. The ureas en- 
closed between the lines should be reproduced in all parte of the 
picture as equal squares. 

Synchronisation Separation. — The border consists of alternate 
black and white rectangles which facilitate recognising inter- 
ference between the picture signals and the synchronisation. 

Low-frequency Response, — -A black rectangle within a white 
rectangle is provided, and in a perfect system it would be repro- 
duced as a rectangle of uniform blackness on a clean white hack- 
ground. At present imperfections in the transmitting system 
result in a slight streaking at the right-hand side of the "black 
area, even with a perfect receiver, but by experience it is possible 
to judge whether the reproduction is abnormal. 

Reflections. — Reflections, which may occur in propagation or 
in the receiving installations, are indicated by two single vertical 
bars, which should bo reproduced without positive or negative 
images at their right-hand sides. The width of these bars re- 
presents a pulse of 0-25 microseconds. 

I ' n {form ity of Focus. — There are four diagonally disposed 
areas of black and white stripes corresponding to a fundamental 
frequency of about 1 Mc/s, and all four should be rosolved uni- 
formly throughout. 

The Test Card " C " radiated by the I.T.A. stations is the same 
except for the identification letters. 

SERVICING PRECAUTIONS 

In order to protect the public from the dangers of mains- 
connected chassis, a number of recommendations have been 
drawn up by tho British Standards Instit ution (BJS. No. 415). 
Tin- most, important sections of the B.S.I, are in regard to the 
measures to bo adopted to prevent tho user from having access 
to " live " parts of tho apparatus. Whether or not any particular 
part is " accessible " is to be determined by consideration of a 
" standard finger " consisting of a metal probe about the size 
and shape of the little finger of a human hand. 

Points which are listed as normally requiring protection in 
receivers using A.C./D.C. technique include : 

(a) The Chassis. The ventilation holes in the back -plate 
should be small enough to prevent access, and the back-plate 
itself should be removable only by means of a tool such as a 
screw -driver. 

(b) Control Spindle*. These should be either of insulating 
material or isolated from tho chassis. Live spindles are con- 
sidered to be acceptable only if the fixing holes for grub screws 
are subsequently filled with insulating material. 

(c) Fixing Screws. All screws securing such parts as the 
chassis, loudspeaker, etc., should be isolated from tho chassis. It 



INSTALLING AND SERVICING 



109 



is good practice to earth other large metal parts, including metal 
ornaments on the cabinet. 

(d) Chassis Outlets. AH outlets from tho chassis, such as 

aerial and earth terminals, should bo isolated from the chassis. 

It. is also recommended thai apparatus should he tested for 
insulation by tho application of a test voltage between the live 
parts and the safety earth provided. 

General Precautions 

(1) Tho chassis of almost all modern receivers arc connected 
to one side of tho mains supplies, and may therefore be " live ". 

(2) Never attempt to measure the voltage at the anode of a 
lino output valve directly, ns the E.H.T. pulses will damage the 
meter. 

(3) Before removing tho picture tube make certain that tho 
K.H.T. condenser is discharged: remember that Aqumlng coating 
may hold its charge for long periods. 

14) Removal of a scanning-coil connection plug while tho re- 
ceiver is operating may cause picture-tube screen burn. 

Mains-connected Chassis 

In normal circumstances the risk of shock is no more pro- 
nounced with mains-connected chassis-type television receivers 
than it would bo with broadcast receivers using similar arrange- 
ments. However, it should be noted that in the case of the 
television receiver, certain routine adjustments such as centring 
tho picture, permanent-magnet focusing, etc., can be carried 
out only with the protective back removed from tho receiver. 
While it is possible to check that the chassis is not above earth 
potential by means of a neon bulb or other simple type of tester, 
reversing the mains plug in its socket where necessary, a safer 
method in tho busy servicing department is always to feed the 
receiver from an isolating transformer, having a low leakage 
inductance. This is not always possible, however, see page 12H. 

The service engineer should ensure that during servicing no 
alterations are made to a receiver that might invalidate the 
manufacturer's safety precautions, and should bring to the 
notice of the owner any deficiencies in receivers which do not 
fully comply with modem practice. 

E.H.T. Voltages 

Where receivers incorporate E.H.T. mains-transformer wind- 
ings, extreme care should be exercised when servicing, as a shock 
from such a power supply may be lethal. Whilst other forms of 
E.H.T. such as line-flyback, K.F. or pulse oscillators, are less 
dangerous, serious bums and shocks are still possible, and due 
respect should be paid to all points at E.H.T. The engineer 
should also be on the look-out for cases where an open circuit in 
the E.H.T. bleeder chain results in the K.H.T. smoothing con- 
densers being left in a charged condition, with the resulting risk 
of bad shocks. 



no 



TELEVISION ENGINEERS' POCKET BOOK 



PRINTED CIRCUITS 



III 



SERVICING PRINTED-CIRCUIT RECEIVERS 

Television receivers in which much of the wiring is in the form 
of printed-circuit panels were introduced in 1956 and have since 
become commonplace. This trend seems likely to continue be- 
cause of the economic advantages to tin* manufacturer in reducing 
labour costs by tho elimination of hand wiring and soldering, the 
ability to reproduce compact units having uniform performance 
and the saving of material. 

Several different techniques of circuit printing an; in use or 
under development. Components, of an orthodox design except 
for special soldering tags, are mounted on one side of a special 
panel of laminated plastic material with the main circuit wiring 
" printed " on the backing side. A thin layer of copper foil is 
bonded on to the wiring side of the panel. The complete 
"circuit "" is i hen printed in an acid-resistant ink on to this 
copper foil. Those parts of the foil which arc not protected by 
the ink are then etched away in an acid bath, leaving the foil to 
act as wiring between the required points: this technique is 
basically similar to that used in the production of printing 
blocks for book illustration. Holes are punched in the panel and 
the components are mounted on tho insulated side wiih their 
connecting tags or wire ends pro tr tiding through the panel. The 
circuit side of the panel is then usually dipped into a bath of 
solder so that all components arc soldered into the circuit in a 
single operation. The wiring panel is usually coated with a 
protective coating. More elaborate forms, with copper foil on 
both sides of the laminated panel, or with coils printed directly 
as spirals (as usual in television cross-over filters) or with somo 
components such as valve-holders on the wiring sido of the 
panel, may also he found, hut the principle remains much the 
same. 

From tho servicing viewpoint tho introduction of the printed 
circuit may be regarded as a mixed blessing. For instance, one 
advantage is that the component identification " K ;l and "' (' 
numbers can be printed alongside the actual component for rapid 
identification, and with such sets all components are usually 
readily accessible without having to dig down through several 
layers of resistors and wires. On the other hand, tracing out 
an unknown circuit can be more difficult, even though the panels 
arc often translucent so that the position of components can be 
observed when looking at the wiring side by bringing n 60-watt 
■ 'lee trie lamp close to the component side of the panel. 

The main difference in the servicing of printed-circuit receivers 
is in the replacement of faulty components, calling as it does for 
greater skUl and care in soldering. Too large or too hot a solder- 
ing-iron may cause blistering and damage to the laminated 
hoard. Very sparing use of solder is also necessary , as other- 
wise it may run between adjacent copper " wires " and be 

djllicult to clear. 






Tools 

The following tools and aids are recommended : 

(1) A low-wattage soldering-iron with a small point or wedge 
bit. Tho ratings should be less than 50 watts, and preferably 
less than 35 watts. 

(2) Supply of 60/40 resin-cored solder. 



PRINTED CIRCUIT 
BOARD 




hairline: crack in foil 
as it appears through 
magnifier and on boarc 



in;, s. crams * Mnammsa Qhtsa to Bxaxxkb 

I'luvri-m \\ hum; IOB H.uu-j.im: O&AflKS, 

(3) Soft wire brush (such as suede-shoo brush). 

(4) Pair of diagonal wire cutters. 

(5) Pair of long-nosed pliers. 

(6) Small wire pick or soldering aid. 

(7) Needle-point probe for circuit testing. 

(8) Magnifying glass for detection of small cracks. 

General Precautions 

(1) Avoid damaging the copper foil. Be careful when re- 
moving components not to cause small breaks in the foil. Should 
a small break occur, this can usually be "' jumped " with molten 
Pokier, larger breaks should be repaired with single-strand 
connecting wire. 

(2) Never apply excessive pressure to the wiring board, this 
■■an easily cause cracks or breaks in the foil. 

(3) Excessive heating from large soldering-irons or due to 
overlong application of a hot iron may cause the bond between the 
board and the copper foil to break or blister. 

(4) When replacing components avoid large deposits of solder. 



12 



TELEVISION ENGINEERS' POCKET BOOK 



These can eusily cause, a short-circuit or intermittent fault, by 
bridging adjacent copper foils. 

(5) When brushing off molten solder small partieles may be 
left sticking to the board. Before installing a new component 
remove these particles with a cloth dipped in solvent. 



Replacing Components 

It is best to clean and tip with solder any new components 
before inserting them through the holes in the laminated base. 
The wired ends of resistors and condensers should be carefully 
trimmed and bent over so that when soldered into position there 
is no tendency for the component to force the copper foil away 
from the base. A method of overcoming this with simpler and 
non-critical circuits is to clip away the defective component with 
wire cutters, leaving as much as possible of the original con- 
necting leads in place and then to shape the leads of the replace- 
ment component into small loops which can be slipped over the 
original leads and soldered into place; if the original leads are 
very short it may prove advisable to cut the old component in 
half with wire cutters and then strip tho component away from 
its internal leads to provide slightly longer connecting wires. It 
should be noted, howovor, that when components are changed 
in more critical circuits, such as where parasitic or spurious 
oscillation is liable to occur with a change of stray capacitance 
or slight change in position of a component, this method of clip- 
ping off" the lead and soldering tho new component to the wire 
ends can result in instability. In such circuits it is better to 
remove the old component completely and to solder the BOW 
component in its place. In all cases where it. is necessary hi 
unsolder wires and lugs on the wiring side of the board, the 
following procedure should be used : 

(1) Heat the connection on the foil side of the panol with a 
small soldering-iron. When the solder becomes molten brush 
it away with a soft wire brush, taking care not to overheat the 
connection, and romoving the iron while brushing away the 
solder. It may require several sequences of heating and brushing 
to remove all tho solder. 

(2) Insert the blade of a knife between the copper foil and the 
bent-over component lead and bend the latter perpendicular to 
the board. It will sometimes be necessary to apply the iron to 
the joint while doing this where the connection has not been 
broken by tho brushing. 

(3) Whilo applying the iron to tho joint, gently " wiggle " 
the i -ot ii po neii t until it comes away from the panel . 

(4) Remove any small particles of solder which may be stick- 
ing to tho protective coating of the circuit board. 

(5) If there is a thin layer of solder left over the hole pierce this 
with the new component wires after heating the solder. 

(6) Place the new component in position and cut the con- 



PRINTED CIRCUITS 



113 



necting lends as necessary. Bend over the ends against the 
copper foil and resolder the joint. 

(7) Finally, recoat the affected area with a protective coating 
.such as polystyrene dope. 

PIN OR NEEDLE SOLDERED ~0 CROCODILE 
CLIP (NEEDLE SHOULD BE BRASS SO THAT 
IT W!LL "TAKE' SOLDER READILY) 




SCREW' OR END MADE CROCODILE 

ADAPTABLE FOR OSCILL05COPF CLIP 

OR TE5TMETER PROBES 

PiC. t. l'i>N.-TIU<TH«N OV \ Xl-'.r.IH.lM'iUXT 

1'nDiiK kor TEsnsi: i>iu.vjt:i> WittiNU Pant.I-S. 

Resistance and component measurements aro usually possible 
from the component side of the board, but should it be necessary 
to work on the wiring side, it should be remembered that the 
protective coating over the foil forms an insulator; this can 
•■■usily be penetrated by using n probe consisting offl biviss needle 
soldered to a crocodile clip, seo Fig, 4. 




Km. 5. Panmro otrccit r i Btraxns kit. 



[SECTION 9] 

SERVICING EQUIPMENT 

by F. Livingston Hogg, M.Brit.I.R.E., A.M.I.E.E, 

Foil many years after broadcasting commenced, receiver ser- 
vicing was carried out in many repair shops with extremely 
1 united test gear. In fact, until the superheterodyne receiver 
compelled the use of a signal generator, far too often the attain- 
ment of a broadcast signal at reasonable volume, etc., was 
considered sufficient, and no other standards were attempted. 
Even now, a skilled engineer can do marvels on a sound receiver 
with a universal meter and a screw-driver. But in television 
this position never existed. Now all dealers have learned that 
some good test equipment enables far more and better work to 
be done on sound sets, yet some are still trying to start on 
television servicing in the bad old way. 

A television receiver is not only far more complex, but it is 
quite impossible to line up most modem sets properly without 
test, gear of a fairly comprehensive nature. This lesson is a 
hard one to learn, but no one should attempt television servicing 
work without a certain reasonable minimum. What this should 
bo is a matter for argument, and the writer proposes to give his 
own personal views with which, doubtless, many experienced 



Fin. ].— avo SKDttli r,i-.xKit.vruit 
Tvi'K in. 
This wiiltyraiHre *iL'iml paoeratai turn- 
villi- :hi K.t". output covering 150 kc.'s to 
'."Ji I U c/s In etr ranges. Thedlalia directly 
calibrated, and toe output may ho oitlior 
niudukiicU (l.ouo ■•>i or umuo.liibii-d. 
An audio froi[iioiii-y otrtput at 1.000 e,'s i* 
nf-.it available. H.F. signal output i* ;it 
ni i-ol i ins impedance via h oontinuotudx 
vuriahle attenuator and four-step decade 
multiplier. 

(.1(71, t.tii.) 



114 




SERVICING EQUIPMENT 



15 




Fir;. 2.— TEUCnSTON WAVEFORM 
AMI AMGNMEXT GKKEHATOH, 
4 -220 Me/s. 

This instrument — Model 94A — 
incorporates a pattern transmitter 

wLicli provides a correct television 
waveform together with an a.m./ 
f.in./e.w. generator, sweep alignment 
L'Piienilor and fixed frequency audio 
signal generator. 
I Titular Ekiiriral Instruments lul.) 



engineers would disagree, in minor particulars, or in emphasis, in 
one direction or the other. However, on fundamentals there is 
fortunately no room for argument. 

Most dealers graduate to television servicing via sound receivers, 
and therefore have some equipment already. When asked for 
a " priority list " in purchasing gear for television, neglecting 
any such items already available, the writer's list would be : 

Absolutely Essential 

1. Signal generator. 

2. Universal meter, 20,000 ohms |>er volt. 

3. Pattern generator, giving a true H.li.l'. I'.T.A. pattern. 
Vrr>/ Dcsiruhlr 

■i. Oscilloscope. 

5. Wobbu later. 

6. Insulation Tester. 

7. Com|mneiii Test Bridge. 
Well Worth WUU 

8. Valve Tester. 

9. E.H.T. Voltmeter. 

10. Signal-strength Meter. 

11. Valve Voltoinnmeter. 

12. Crystal Calibrator. 

This list, is not exhaustive but is only a guide. 

When investing in test gear, it must always bo borne in 
mind that the criterion is that the equipment should earn its 
keep. On the other hand, equipment unintelligent ly used will 
never pay. To be satisfactory, tho gear must be reliable and 
always give the same reading in similar circumstances. Itniust 
bo reasonably easy to handle, so that it does not mislead. Never- 
theless, unless test gear is handled and used wisely it ran lie a 
time waster. Hours can be spent on the niceties of alignment, 
which, although they may appear to have considerable influence 
on tho measured responses, hardly alter picture quality one iota. 
A good engineer is made efficient and productive by good test 
gear, but good tost gear will not make a bad engineer into a 
good one. But, what is more important, a trainee engineer, 



116 



TELEVISION ENGINEERS' POCKET BOOK 





SERVICING EQUIPMENT 



117 



VI » 



90. j.— Thk " i"i:i-j;vj:x *' Tviu: SSfl, v t'uifr.uii.r. Mt i.n-i'i im>M 

TBwrmoa ti«t ehsswukt. 

This instrument contains in one unil 151 in. •■: DJ in. x SJ in. n wobbulator 
(sweep ii|i to 12 Mc/s iiini provision fur crystal >eiliii"p); an alimlituiie-iuodulnled 
signal generator (two ranges 8-7<J Ale's ami 188-2M Me/s, with 5-JIi',/s crystal check 
calibrator; a pattern generator providing a pattern constating of three horizontal 

lilm'k bar* on ilirci' vertical Mack bar.-; an audio te-a simui] (."■ kc/-.i: ail oscilloscope 

with iniili-iti Sf amplifier and time-base; an kji.t. vtutmeter; m A.O./D.O, rnlve 
voltmeter; sod an bi <Ws lin tpot transformer tester . 

trained to use good equipment properly, has a better chance of 
becoming an efficient engineer than if he has little gear and has 
to acquire more instinctive skill before ho can show results. 

There are many manufacturers of tost gear, and their products 



Fig. *.— Swkal Qwmuaxut 

TYI'K Jv.'i. 

The frequency range is 100 
kc/s to 100 M*c/s on funda- 
mentals. Tnternul cuodnlation 
at 400 c/s 30 per cent ia avail- 
able, and it may be modulated 
from nn external sour re, 'Die 
B.F. output is continuously 
variable from 1 jtV to 100 uiV, 
and a constant output of 
approximately 1 V at W ohms 
impednnee is also available. 
For Baud 111 work, an alter- 
native model, type S3, lin.-i been 
introduced with a range of 151) 
ko/B bo 890 Mc/s, 

(Atlnincn Cimiftimerttn f,hl.) 




r m itfB, us for every other commodity, from good to bad. It would 
be possible to make a fairly comprehensive list of all available 
apparatus which would be oidy a catalogue, of little help to the 
engineer. The writor therefore proposes to outline the desirable 
features of tho various types of instrument mentioned above, 
and then to give a few selected examples from recent production. 
These examples are those ho has used and knows to be satis- 
factory, but many other satisfactory instruments aro not men- 
tioned. There are also others. ... It is not proposed to 
discuss those instruments which are maiidy used in develop- 
ment laboratories, but to consider only instruments of types 
normally supplied for servicemen's use. 

Signal Generators 

At quo time these could bo divided into two classes, more 
aptly named test oscillators and standard signal generators. 
The former consists of a tunable oscillator, which can be modu- 
lated, together with means of attenuating tho R.F. output. 
The seeond class has all these features, but also has a means of 
sotting tho output level to a known and repeat able value on all 
frequencies. The test-oscillator output varios, perhaps widely, 
with frequency, rendering comparative tests sometimes quite 
misleading. Years ago the difference in performance was very 
groat, but clever design has produced most efficient test oscilla- 
tors with remarkably constant output which enables quite good 
relative checks to be made. It is necessary to stress that the 
signal generator must tune to the fundamental television fre- 
quencies. In tho writer's opinion the suggestion of using 
harmonics is a diabolical one designed to mislead the unskilled 
and unwary! 

It would bo preferable if service stations used metered signal 
generators exclusively, but the modern cheaper variety is so 
good, in its best examples, that cost often overrides. It is, 
however, suggosted that all service stations should have at least 
one standard metered generator to servo as a check against 
deterioration of standards of performance. 

One essential feature of a signal source is good frequency 
stability and resetting accuracy. Unfortunately the require- 
ments of television sots working on single sideband are very 
high, in fact higher than can be reasonably expected from the 
most expensive laboratory generator. No tunable oscillator 
of normal type can be expected to hold over a long period to as 
good as 0-1 per cent, including resetting accuracy, and few 
manufacturers guarantee better than 1 per cent. The variation 
of stability of the television set will absorb most of tho tolerance 
available, therefore the source stability should be much better 
so that the error from it is negligible. This means that it should 
be certainly within 20-30 kc/s of nominal, which is round 003- 
0-04 per cent. 

Clearly if wo demand such stability from our signal generators 
we shall either delude ourselves or bo disappointod. 



118 



TELEVISION ENGINEERS' POCKET BOOK 







I I'.. .">. -TKLKQUIPMBOT W0/-I4 
I'ATTKKK. 

This photograph shows non- 
lini':irity anil ringing. The 
number of vertical lines is ad- 
justable i ruin about 5-20, 



Tlie simplest way of overcoming this is to beat the carrier 
of tho signal generator with the station, so synchronising them, 
and noting how much the generator deviates and how it drifts 
during working periods, A little experience soon shows how 
frequently this must be done, and how closely tho required 
channel van be set up without reference to the station. This is 
not- an ideal method, am! sometimes it is not possible to use it. 
The ideal method is a crystal calibrated wavometer or oscillator, 
which will be considered later. 




Pig, a, tiik " iiii.TisiiN'eH " .Mw.Ti-UAXia.; Tkst Mktkk. 
The Internal oonstrootioa, aaiiig printed ciroaltry, Is shown in the lower rjght-lumd 
portion of t,he i Hasina ion. Benaitivity Ii 10,000 ohms/volt uu D.C. tangos. 

t'.iiy/, l.ttt.) 



SERVICING EQUIPMENT 



119 



Universal Meters 

The ubiquitous Avomoter hero comes to mind, although there 
are other good instruments available. For television work it is 
often essential to have a high-resistance meter of 2IUHHI ohms 
per volt, such as the Avo Model 8. However, some manu- 
facturers' service data still calls for a 1,000-ohms per volt meter 
such as the Avo Model 7, so that it is normally necessary to have 
both types at hand. 

In choosing an instrument it is very important (o be sure 
i hat good overload protection is incorporated. The extra 
cost is saved in every shop sooner or later. 

Pattern Generators 

A television pattern 
generator should be used 
not only when tho actual 
transmissions arc not on the 
air, but at all times. The 
real picture content is 
continually varying, and 
is somotimes of variable 
quality. It is also subject 
to inlet Terence. A constant 
pattern is far more satis- 
factory for servicing, and is 
not misleading (or even in- 
teresting ! At test match 
times , . .). Tho statement 
t hat of course the final cri- 
terion is what the actual 
transmission looks like, is 
not as all embracing as 
might appear. 

This assumes that I he 
pattern generator and I he 
actual transmission have 
equal effect on the receiver 
as to synchronising, etc. 
dad 




AVO " I SIVKKSAI. TKST MKTKK. 
i .}>:<•. Ltd,) 




Tin. 8. Mettrtiv TPG.il Pati'min. 

(n) 20,250 -c/'s master oscillator reiural 
e vertical bar unit line blunkiiig pulse. 

(d) gOO-ko/a vertical teres bass. 

(fj 2B0-C/B horizontal black burs and 
™ frame frequency blanking poise. 



120 



TELEVISION ENGINEERS' POCKET BOOK 



TPG39n_ 



100 

n 



39fl SIGNAL 

^GENERATOR 



^wv^^r 



39tt 



FlO. 3. — T-PAJ) Foil MlXINli SIUNAI. 
tiKN'KKAToli OUTl'L'lH. 



TV. SET 
t 



-Vow tho picturo waveform is extremely complex, and this 
complexity is necessary. A television pattern generator must 
therefore give a fully synchronised interlaced pattern having 
all tho characteristics of the real transmission, A receiver 
adjusted on such a pattern generator will then immediately 
give a correct picture on the station, provided that the correct 
K.F. level is used. This applies to all phases of servicing adjust- 
ments — Linearity, aspect ratio, interlace, hum level, sound on 
vision, etc. All can lx* checked with a good pattern generator 
with certainty that all will be well when the station conies on. 

But if tho pattern generator does not give exactly the correct 
waveform; if it does not incorporate interlace, or have lino and 
frame frequencies derived from a single oscillator, or half-lino 
pulses, or the front and back porches, or any such feature, it is 
useless and should not be admitted to the service station. The 
mason for this drastic statement is that such an instrument. 




Fit;, 10. Hon) i. 1052 nouBM*- 

I1KAM OsenXoCKAl'ii, 

A f;encr:il -purpose instrument 
providing two identical amplify- 
ing channels with a maximum 
gun of 2,000 and an upper ire- 
qnency response of y Hem. Thfl 
repetitive or triggered ame-baaa 
baa a sweep duration from 20o 
milliseconds to 5 mieroseeoiids. 
The instrument will operate from 
power supplies of the various 
I'rcuimHcs and voltages en- 
conntared in the A rmed Ser\ toes 
or tram standard eivil supply 

ciuiiiis. 

(COMOT tit,\tritutt al.i, Ltd. I 












■ 



SERVICING EQUIPMENT 



121 



I !'..!0 (((>■— EUHABT3 ! ' ! 

405 TKLEVlSlu.V SlG- 

HAL CKXKKATOR. 

A complete range of 

patterns, together with 

correct sync, pulses, is 

provided." Simultaneous 

id and vision H.I-. 

signal*, arc given, the 
ranges being 40-70 Mc/s 
and 174-210 Mc/s. 
(Waveform t, Ltd.) 




gives misleading results, which must be avoided at all costs. 
On such a pattern generator any adjustment made cannot be 
guaranteed correct for the actual transmission — it may look 
right on the pattern generator and be wrong on transmission, 
or vice versa. Some receivers will in fact only function properly 
when fed with an interlaced pattern. 

The writer makes no apology or attempt to conceal tho bee 
in his bonnet on this matter. He considers that no one should 
liavo tho temerity to attempt television servicing commercially 
without a pattern generator, and, furthermore, that any pattern 
generator not conforming fully lo R.B.C standards should not bo 
allowed on the premises ! 

It may be mentioned at this juncture that the optimum 
pattern generator for use on sets with flywheel synchronisation is 
not the optimum for sets without this facility. Jn order to cope 
with both cases a compromise has to be adopted, which leaves so 
little to be desired that most would be unaware of the deficiency. 

Oscilloscopes 

There is much difference of opinion over oscilloscopes, some 
finding them of inestimable value, and others not. Probably 
the reason for this lies partly in the handling, and in knowing 
how to interpret the results. If the 'scope amplifiers have a 
reasonably high gain, and the input of tho 'scope is connected to 
a high-impedance ciietiil, the resulting traco may bo modified 



122 



TELEVISION ENGINEERS' POCKET BOOK 



+ 3d 

NORMAL 


3 / 
































SIGNAL 
-3db 
-6db 

-20db 

NO StGiMAL 


































i 
















\ 

































FREQUENCY 
.CALIBRATION . 



Kt«. u. — Typical QtuncULB Layout. 



or completely upset by spuri- 
diis pick -up, mains hum, etc. 
The attachment of tho 'scope 
input may also disturb tho 
operation of the circuit under 
test. Only experience can 
show how to overcome these 
difficulties in different cases. 
In tho writer's opinion the 
greatest value of a 'scope is in 
conjunction with a wobbula- 
tnr. 

Some points to look for in 
choosing a 'scope are : good 
sensitivity variable over a wide range, wide frequency range and 
a good I incur time-base. For many purposes a good H.F. response 
is unnecessary, but. it is invaluable when checking a pattern 
generator, or when looking for spurious H.F. oscillations on L.F. 
circuits. 

Several useful instruments are made by Cossor. Their 
Model 1039M is extremely small and light. It has a 2$-in. 
single-beam tube, but because of its small size, tho L.F. and U.K. 
response is limited. Model 1035 is a much larger instrument 
having a 4-in. double- beam tube, with calibrated time and voltago 
scales and many other facilities. The T/eloquipment Model fn'ii is 
remarkably light considering its 4-in. single-beam tube. It is 
notable for its wide H.F. response, covering the wholo face of I he 
tube. These two last instrument's are particularly convenient 
for viewing wavoforms from pattern generators. 

Wobbulators 

A wobbulator, or frequency modulated oscillator, together 

with an oscilloscope, is undoubtedly far the best apparatus for 
lining up television sets to the correct band-width accurately and 
quickly. As usual, howovor, there are snags. The apparatus 



O 



OSCILLOSCOPE 



nTsCREENE 

fl LEAD ^ 



WOBBULATOR 



T.V. 
RECEIVER 



AE. SOCKET 



5O-10OK RESISTOR 

=t-WAr-x*y^CL\PS TO 

c ,C.R.T. ON 

___&£ RECEIVER 



N.U. 



ma, i-'.— woiiuuiiATOB O Mumumj wa, 

-&eritss mirth condensers to bu liUwl where necesntnr. 



I 



SERVICING EQUIPMENT 



123 





in;. 18.— {above} T.m.tm 80,000 

nll.MS vol.T t'OCKBT 't'KSTM KTKIi 
1M1 (right) Q-SCAN 0SCILLO,K»rK 
R)H TEUtViaiOS IlKi'KIVKll Al.KiX- 
MKNT ILV M AlH-liM iNSTtll MKVIS. 



iiiust be right, it must be connected appropriately and must be 
used correctly. Mutters have not been helped in that makers' 
i nsf ruction books have not emphasised the pit fulls sufficiently. 

In tho first place, optimum alignment should bo made at 
the working sensitivity of the receiver, or at a lower input 
signal. As most reasonably priced wobbulators are Dot fitted with 
iii-i'iimte at tenuators, this sumrtiuies lends to trouble. Secondly, 
the oscilloscope must be connected in such a way as not to 
affect the operation of tho receiver. Practically, the output 
is normally taken from grid or cathode of the cathode-ray tube. 
If a clip is fitted to a resistor of ,50,000 ohms upwards, which is 
connected in series with the conductor of a screened cable, 
with a further clip from the screening for earthing, this can 
bo connected to the 'scope and will not usually upset the receiver 
at all. If it does, slight, readjustment of leads or resistance 
should remove the trouble. Next factor of importance is the 
sweep frequency. This must be low; 16| o/fl (\ mains fre- 
quency) is goodj 2;5 c's should be the maximum. This is on the 
limit of a small oscilloscope (anil some larger ones), which 
distorts the waveform if the frequency is too low for it. It is 
also good to connect a condenser of about 0-01 n~F across the 
input to the 'scope amplifier. 

The method of operation of a wobbulator differs somewhat 
with different sets. Usually if the set is noi far from alignment, 
injection into the aerial or at I.F., and alignment in order working 



124 



TELEVISION ENGINEERS - POCKET BOOK 




FlC. It.— 0OB908 " TELK- 
c.|tKC£ "■ 

iiiiivrtly Uinoil vision rc- 
Bponse curve taken from aj 
tyjiirnl sinale skic:l>.unl re- 
ceiver. The marker pip is at 
vision carrier frequency. 



from the circuits nearest tho 2nd detector through finally to the 
aerial, is the drill. Sometimes it is necessary to inject into each 
grid in turn, dealing only with the immediately subsequent 
circuits in turn, arriving finally at the aerial end. Each typo 
of receiver has its own idiosyncrasies, but experience is the 
only way to find the optimum method in any particular case. 
It is a good thing to make a graticule showing the calibration of 
the instrument in frequency in the horizontal (X) direction and 
calibrated in db in the vertical (Y) direction, say at 3 db up, 
3 db, 6 db and 20 db down on i In- normal defied ion (3 db down 
is 70 per cent. db down is f>U j ■<_■ i- cent, 'JO dli down is JO per 
cent of normal, but 3 db up is 140 por cent). Here is a wonderful 
opportunity for time-wasting, trying to get a perfect curve. 
It must be remembered that getting the carrier at the 3-db or 
6-db point is important on a single-sideband set, but that dips 
or rises of 2 or 3 db over the band will hardly affect tho picture. 
As long as the carrier is right and the band-width adoquato small 
irregularities are of no consequence. 

Another important thing is tho frequency sotting of the 
wobbulator. If a signal from tho generator is injected into the 
wobbulator (if provided with a suitable terminal) or through a 
T-pad with the wobbulator, a kink will be seon on the trace 
at tho frequency corresponding to tho generator frequency. 
Tho 0-01-/xF condenser across tho 'scope will prevent the high- 
frequency beats from widening the trace, and enable an accurate 
adjustment to be made. Care must be token that- the signal- 
generator signal is not too strong, or it may modify the traco 



FlU. 15.— " THJjK-L'HECK " Muiu-x 

1380. 

Alignment is carried out by u^iiit" 
the i list rt uncut in conjunction with 
uu oosStoscopa, The frequency 
modulation sweep i> " Wc -, and the 

carrier frequency U 7-70 Me/.-. J •<■■•■ 

visiutl 19 luuile for (tin inject ion of a 

frequency marker nip from a signal 
generator. Other models are avail- 
able having a sweep of, lo Mc/s and 
covering both Band I and Bond III. 

[Cossor Instrumeius, Ltd.) 




SERVICING EQUIPMENT 



125 



Fid. 



10, — OOSSOR 

CHECK " 



■ Tl'l.K- 




A double- beam tube em- 
ployed for the obsarrot ion of 
both the sound and virion 
response curves of a single 
sideband r ece ive * simultane- 
ously. The son ud channel is 
iix-orrcuily aligned in this 
instance. 



from the receiver, and so mislead. A better method is to feed 
from the T-pad into a crystal rectifier with a load of say 10,000 
ohms in series. Tho 'scopo (with 0-01-jtF condenser) is then 
connected across this 10,000-ohm resistor. The marker can then 
be used to check the linearity of sweep and calibrate a graticule. 
A wobbulator correctly used often shortens alignment time 
to between one-tenth and one-lift h of the time taken by ordinary 

methods, including dampers, 
otc. Tho technique of using 
it is, however, of vital import- 

II I ICC. 

Two commercial wobbu- 
lators are the Cossor Tolecheck 
and the Marconi Instruments' 
" Q " Scan. 

The Tolecheck covers 7-70 
Mc/s, and is frequency modu- 
lated ±3*5 Mc/s by the time- 
base voltage from the oscillo- 
scope used for viewing. On 
Cossor oscilloscopes there is 
a terminal from which this 
voltago (100 V or so) can be 
obtained. When using other 
makes of oscilloscope care 
must bo taken that suitable 
connections are made. For 
instance, when using a 'scope 
with a push-pull amplified 
time-base, such as the Tele- 
quipment Model 520, the volt- 
age input to the amplifier is 
too low for satisfactory use. 
The necessary voltage is avail- 
able on the plate plug at the 
re; n- of" the instrument, and 




17, — Moron 1S0B Ixsri.ATtox 

maa 

A mains operated ohmmetez for worfc- 

slm|, k^u nii.l ioi«|ioiient cl'O'kiiii.'. 

McftBures up to 1000 MP. at a best 
■ isttfti ol BOO volt**. 

(Taylor Electrical Instruments Ltd.) 



126 



TELEVISION ENGINEERS' POCKET BOOK 
.50 pa 



X 



9 MEG. 



PRESS 
SWITCH 

— I 



Uy^J 



h'Jii. 18. — tSSOLATIOS Tkstek. 
Culib ration of meter : 
Current (pA) . M 48 »-fl .12-1 2S-1 28-6 IK-8 15-6 

ltesistauue (lit!) .012 5 J 10 18 2u 






•<I -ll 

too 



200 



should be taken, through a blocking condenser 0*25-2 /ttF, to tho 
Telecheck. 

The Marconi " Q " Sean incorporates the necessary oscillo- 
scope, which can bo used independently if desired. The fre- 
quency range is 10 '.)"> Mc;'a, and the maximum sweep is 5 Mc/s 
total, which is ideal for single-sideband receivers. 

A very comprehensive survey of wobbulator techniques with 
special reference to the Teleeheek was made by W. I. Flack in 
an article in Elect-Heal tfc Radio Trading, July 1953, reprints of 
which are available on request from Messrs. A, C. Cossor Ltd. 

Insulation Testers 

A large proportion of faulty components in television receivers 
have faulty insulation, and the wrilor believes that much in- 
ferior performance can be attributed to loaky condensers in 
particular. In tho writer's laboratory all such components 
are tested on SOU V D.C., with quite startling results. For such 
tests an instrument giving a maximum reading of 200 megohms 
is the minimum l-equirement, but high accuracy is not needed. 
The Wee Megger needs no introduction, and particularly when 
extreme portability is required, such types with hand-driven 
D.C. generators havo no rivals. A very convenient mains- 
operated device is the Taylor Model 130H, which derives the 
500- volt supply from the mains. It is also possible to make a 
very simple instrument using t.'ight 0TA-V denl'-aid-iype. butteries, 
a few resistors and a 50-aA meter. The battery drain never 
exceeds about 50 /*A, and the life is extremely long; some have 
been in use for seven years before running down. 

Component Test Bridges 

Many faults arise due to components, mainly condensers mid 
resistances, changing in valuo. Theso are best cheeked on a 
bridge. The requirements aro that tho full probable) range of 
values of capacity and resistance can be measured reasonably 
accurately, say to within f> per cent at worst. Kven this is a 
fairly stringent requirement, it is sometimes an advantage 
to have the facility to measure inductance as well, but for a 
number of reasons this facility is not as useful aa it would appear. 

Three good instruments, each with their own special features, 



SERVICING EQUIPMENT 



127 




Fn;. 19.— OAPAOIXOn Ana- 

I.VSKH AMi ItKSISTAXeH 
BIUDGE, XYI'K ORBS. 

This test bridge covers ranges 
■:<i ji K to 500 (iF; 50 ohms bj 
l'ti i Megohms. Jl measures 
capacitance by means of a 
Wieu bridge; ttie resistance of 
all types of carbon and wiro- 
wound resistors; the leakage 
rirsi stance of paper and elcrtro- 
lytic capacitors and all types of 
insulation, 33-600 V, by flush- 
ing n con . H d Lrecxly indie al ea 
leaky, shorted, low-capacity, 
high-capacity aud high-power- 
faetor capacitors of both 
usual and intermittent types. 
Measurements arc made di- 
rectly, and no calculations arc 
necessary. 

i.l. //. Uimt (Capacitors) Ltd.) 



are the E.M.I. QD.211 Component Bridge, the Avo Universal 
rest Bridge, and the Hunt Resislanee and Capaeitv bridge. 
Valve Testers 

A valve tester can be a great help, but it must be borno in 
mind that it is no reflection on tho instrument that it will un- 
doubtedly fail to reveal some valve faults. If it. were not for 
this, a valve tester would rato higher in the priority list. The 
writer personally prefers a valve characteristic meter, which en- 
ables values to be measured on a meter, which is perhaps an under- 
standable bias ! 

E.H.T. Voltmeters 

The measurement of E.H.T. Voltages is a very dilTk-ult prob- 
lem. Very little current is available for a meter, and leakage 



l' Hi. 20.— IlHill-SPKKIl 

Klkcthoxic Valvk 
Tkstkr. 

All electrode potentials 
are automatically applied 
by the insertion of the 
appropriate perforated 
test card In a multiple 
;:.ite switch. The tests 
include: filament or 
heater continuity; elec- 
trode insolation with anil 
without JLT. applied ; 
heater- cathode insula- 
tion ; grid current ; 
'mission. 



( Mellaril f.td.) 




128 



TELEVISION ENGINEERS' POCKET BOOK 






SERVICING EQUIPMENT 



129 




Kit;, 



21.— PnATiAMP "RLECTnoOTATIP 
VOLTMIiTliH. 



Available in three ranf.'i>;= : I 3 k\ 
k.{ .. D.O, ."-10 kV A.C, U.C., and 5-18 
k.V D.U. or 5-10 fcV A.C A direct- 
reeling Liistrtiment with ;v 3-8CC. perioil. 
The lamp can he openitcc! from A.C. 
mains or -1-V buttery. 

(W. O. Pye <fc Co. ltd. 



due to humidity is a particular snag. Two methods, which 
can be satisfactory, aro to uso an electrostatic, motor, or a very 
low current (20-25 pA) meter with high series resistance. Both 
methods are unfortunately costly. Some results can be obtained 
by connecting say three 5-kVA electrostatic meters in series, and 
summing the readings, but great circumspection is required. 

The Pye Scalamp E.S.V. is ideal for this purpose. Other 
methods than the above have been proposed, but, for reasons 
such as aro given above, cannot be commended. 

Signal-strength Meters 

Such a dovieo as a signal -strength meter is valuable in two 
main connections. Firstly, in assessing strength of signal at 
new locations, and secondly, in testing existing aerial installa- 
tions. It is important to mako such measurements not on 
picture content, hut on peak white or synchronising levels. 

Valve Voltohmmeters and Crystal Calibrators 

Valve voltuhmmetcrs do approximately all that a Universal 
Tost Meter will do, unci much besides. Unfortunately they are 
fairly delicate and a shade tricky to handle. If such difficulties 
;in- appreciated, and care used in getting results, they aro most 
useful adjuncts to any test shop. Tho uses are legion, but good 
engineering skill or supervision is needed. The lack of these 
and a failure to appreciate tho limitations of technique have 
given this typo of instrument a bad name not altogether deserved. 

Good examples are : Tho Avo Electronic Test Meter covering 
250 mV to 250 V D.C.. 25 ,iA to 1 A D.C., 1-250 V A.C, and 
1 6- 1 0,000 ohms mid -scale resistance, and the Marconi Instruments' 
T.F.8S7A Valve Voltohmmoter. which has ranges of 5-250 V 
U.C., 5-125 V A.C. and 12-5-50,000 ohms mid-scalo resistance. 

As stated earlier under " Signal Generators " a crystal calibrator 
or waveineter is a great help. Unfortunately tho frequencies 
required aro all awkward, except that of London, so that if 
one tries to uso tho harmonies of a single crystal it must be 0-25 
Mc/s. This is too low for convenience. The only commercial 
instrument now available that the writer has come across is the 









; 



E.M.I, spot frequency marker AD/U405, which gives 1-M.c/s 
pips throughout the range. In some cases this is sufficient, 
but in others the dial of the signal generator cannot be read 
accurately enough. U.S. surplus wavemetors BC.22I or TE.149, 
if properly recalibrated and adjusted, can bo used, or, particularly 
if only ono channel is required, a simple crystal harmonic 
generator oscillator can be made up. 

Conclusion 

Instruments are not tho only items of importance in a repair 
shop. Tho obvious ones of good bench space and so on need no 
b1 rearing, Kut a point overlooked too often is that television 
sets are lethal. Every test position must be equipped in accord- 
ance with the Factory Acts and regulations. 

An essential is a properly scrooned double-wound transformer 
i>r 1 to 1 ratio. Tho screen should be well earthed. An earth 
bar may be fitted at tho back of the bench, but it must only be 
connected to oarth through a series condenser of high tost voltage 
and not more than 002 /u.F capacity. Where oarth terminals 
of instruments would be connected effectively direct to tho mains 
via alive chassis, isolating condensers of similar type aro ossontial. 

The whole load of the bench or test position, for ono engineer 
only, should come from one t ransformcr secondary, connected to a 
multiplicity of sockets of all likoly types and sixes. Two engineers 
should never share a transformer— they could got two chassis 
not very far apart connected to opposite sides of tho A.C. supply. 
This problem must be dealt with according to circumstances. 
* # * 

While the use? of a double-wound isolating transformer having 
low leakage inductance lias much to recommend it on the 
grounds of safety, it is unfortunate thai some telrvi.-ion-recoiver 
fault svmpfoms'ainl adjustments are affeeted by the 086 of SUOfl 

a transformer. For this reason it is often necessary to operate 
the receiver directly from the mains supply, and in such efr- 
cumstanccs the best safeguard is to ensure by chocking with 
.i neon bulb or similar tester of known reliability that the 
chassis is always connect e. I to the neutral and not (lie live mains 
lead, taking care to ro-check each time thai the mains load is 
re- connected. , 

The introduction of kits using priulcd-circuit panels oilers an 
economical method of building up a range of servicing instru- 
ments. The home construction of good test instruments has in 
the past beon regarded as a most tricky operation owing to the 
likelihood of even minor differences of lay-out and construction 
leading to considerable variations in results and in calibration. 
In those new kits this difficulty is overcome by the use of prin ted - 
circuit panels giving a degree of consistency between instruments 
difficult to achieve by other means. These kits, including os- 
cilloscopes, valve and multi-range testmetors, signal generators, 
etc., are supplied with stop-by-step assembly instructions. 
£ 



RECEIVER AERIALS 



131 



[SECTION 10J 

RECEIVER AERIALS 

Tuk requirements of an aorial system for television reception 
are considerably more exacting than those for normal broad- 
casting purposes. This is because of : 

(1) the lower power, and correspondingly lower field 
strength of television stations; 

(2) the greater band-width required, and consequent lower 
gain per stage in the receiver ; 

(3) the higher circuit and insulation losses, and greater 
valve noise on V.H.F. ; 

(4) (.lie greater susceptibility of V.H.F. signals to electrical 
and ignition interference; 

(.">) (he necessity to avoid receiving transmissions by 
multiple paths in order to reduce il ghost " images; 

(G) the greater susceptibility of the eye, as compared with 
ear, to interference and signal variations. 

On tlie other hand, it should be recognised that (ho use of a 
directional aerial system., tuned for dpi iimiiii piek-up on a limited 
range of frequencies, and coupled to the receiver by a matched 
transmission line, represents basically a much more efficient 
type oi arrangement than is customarily employed for broadcast 
reception. 

The choice of an aerial and transmission line for any particular 
insinuation will depend upon the distance from the transmitter: 
its height and freedom Tram screening; the level of local inter- 
ference; the length of feeder cable necessary; the sensitivity 
and input impedance of the receiver; mid any restriction's 
imposed by the landlord or local authorities, 'it should he 
emphasised, however, that wlion planning an installation it is 
belter to provide loo much rather than too little signal input; 
for while if is a simple matter to incorporate an attenuator pad 
U3 the feeder to reduce an excessive signal, the raising of" the 
signal level by even a few decibels may require the complete 
re-planning of the installation. Unlike valve amplification, 
additional gam in the aerial does not introduce " noiso ". 

Aerial Terminology 

ihiff-wuvc Dipole. The fundamental form r a resonant 
aerial is a single conductor with an electrical length equal to half 
t lie wavelength on which optimum reception is required 

Aer-ud Impedance. The natural impedance varies with the 
current distribution along the aerial. For a half-wave dipole the 

130 



impedance at tho ends is several thousand ohms, and approx i mately 
72 ohms at the centre. Additional director or reflector elements 
will tend to reduce tho impedance, and on a four-element array 
the centre impedance may be of the order of 25 ohms. 

Fieltl. Strength Pattern. The variation of reception around 
an aerial is normally shown graphically by means of ,l polar 
diagrams"', which are circular charts with the angle (0-360") 
indicating tho direction for which tho signal strength is plotted, 
and the length of the radial arm indicating its magnitude. 

Aerial Gain. This term expresses the increase in signal 
strength for one type over another, a standard half-wavo dipole 
usually being adopted for reference purposes. The gain is 
measured in the direction of optimum reception, and is usually 
expressed in decibels. Thus an aerial with a 6-db gain would 
provide double the voltage, or four times the power, across the 
input circuit of the receiver. 

Front-to -back Ratio. This is the term used to denote the ratio 
between the pick-up, when tho aerial is orientated for optimum 
response, to that for tho position of minimum response. It is 
usually expressed in decibels. 

Decibel (do). The oue-tonth part of a bid, this latter beinjr 
the common logarithm of the ratio between a second power, or 
intensity, and a first one. The decibel, therefore, is a unit for 
expressing the gain or loss in an electrical or acoustic circuit 
when the input, is known, or of defining any power iu relation 
to a predetermined basic level of that power. 

The Dipole 

This, tho simplest form of tuned aerial, consists in practice of 
a metal rod, divided at its centre by an air gap of about 1 in. for 
connection of the transmission line, and of overall length approxi- 
mately half that of tho wavelength on which optimum reception 
is required. Owing to end effect, the length is not an exact 
half- wave. Tho formula below will enable tho length to be 
determined : 

. ,. . 5908 x k 

Length (m.) - f^rjinoy {Mc/s) 

where k is a factor depending upon the ratio of half-wavelength 
to the diameter of the aerial element, usually varying between 
0-92 and 0-98. So as to ensure that the band-width of the aerial 
is sufficient, the length/diameter ratio should he less than 400. 
The impedance at the centre is approximately 72 ohms, but this 
may be affected by the presence of nearby objects or additional 
elements. 

The signal being received produces a standing wave in the 
dipole. which results in there being zero current but maximum 
voltage at the extreme cuds of the rod, and maximum current 
but, low voltage at the conlro. The signals are fed to the receiver 
via a feeder cable which in order to minimise loss must be fairly 



132 



TELEVISION ENGINEERS' POCKET BOOK 

Taule 10.1. — Typical. Dimensions of Television 
Aerials 



RECEIVER AERIALS 



133 



Channel 


Minn 
Freq, 


I) i pole 


Dittdor 


IlcflcClOT 


X pitting 

iA" 
/I, «'«. 




(.Me/*) 


ft. in. 


ft. in. 


ft. in. 


1 


43-0 


10 7 


In 1 


11 1 


8 «.l 


2 


M 


a 3 


8 0} 


!) Si 


4 U 


3 


55 


8 5 


S II 


s ]ll 


4 5 


4 


GO 


T Bj 


7 4 


a i 


4 01 


a 


65 


7 1 


6 ;i 


7 5 




6 
7 


17S 
183 


2 7J 
S 6J 


2 6 
2 5 


8 
2 8 


1 41 

1 4' 


8 


l.S.s 


•> :, \ 


2 1 


9 7 


l :;'. 


'.i 


1 83 


■J V. 


2 3 


2 6 


1 V 


Id 


108 


2 31 


2 2.J 


2 5 


1 2i 


] 1 


203 


2 3 


2 2 


■: -\- 


1 2' 


12 


208 


2 2.1 


2 1.! 


2 4 


1 3 


13 


213 


2 2 


2 1 


2 3 


1 lj 



* Halve these dimensions for J A spacing. 
Auto 'Hie exjwl dimensions are idlwlci] hv the ratio of diameter to overall 
length, and so will vary slightly according to the tubing used. 

accurately matched in impedance to that existing at the point of 
connection to the aerial system, and also to the input circuit <>[' 
the receiver. Where the eo-axial typo of feeder is employed, the 
centre conductor should ho connected to the upper half of the 
rod and the outer conductor to the lower section. 

The simple half- wave aerial is intended for use in areas where 
reception conditions are good; where interference is to be met 
With, its non-directional properties arc against its use. 

Dipole Plus Reflector : the H Type 

By mounting another slightly longer metal rod at one-quarter 
or one-oighth of the signal wavelength behind the dipole. the 
aerial can bo made directional. Typical dipole and reflector 
lengths are given in Tablo 10.1. 

The spacing of the two rods is not critical; typical spacings 
are 5 ft. 6 in. London, and 4 ft. Birmingham. Tho spacing 
distance, however, will affect the dipole impedance and its 
polar diagram. Tho rod has no electrical connection with either 
the dipole or any other part of the aerial system. 

The reflector increases the pick-up efficiency of the dipole in 
tho forward direction (as a rule it is about 5 db better than tho 
standard dipole) and reduces it in the rear, the front-to-back 
ratio being of the order of 9 db. Where inieiferei.ee radiation is 
strong and lies behind anil not across the transmitted signal's 
path, effective screening can bo achieved by putting the reflector 
between the interference source and the aerial proper. When Ibis 
has been done, the aerial may no longer bo " pointing " towards 
the transmitter, but this makes little difference, provided that 
the direction of the aerial is not more than 30° from the correct 
position. 






From a signal-strength viewpoint, and also as regards inter- 
ference free signals, the H type aerial should prove satisfactory 
in all but the most distant and difficult locations. 

Directors 

A director is an clement of slightly less length than the dipole, 
and serves to increase the forward gain of the system. Director 
lengths can be determined by using the following formula : 

Length (m.) . Frequency (i ]^j 

X Aerials 

This design represents modifications to tho basic H type 
aerial, and offers certain advantages in ease of fixing, etc. 

Tatile 10.2.— Properties of Various Types of 
Band I Television Aeui ai.s 



TYPE OF AERIAL 


RELATIVE CAIN 
TO A DIPOLE 


r 

POLAR DIAGRAM 
(RELATIVE* 


r 

•ROBABLE MAXIMUM 
RANGE IMII CSV 1 


OCCASIONAL 
«ANCE (MILES) 


DIPOLE 


Odfe 

(i.e.TKEBEISKOGAIN- 
MHtl PICK UP IS Hi) 


o 


16 


50 


i 
V DIPOLE 


-6-Odb 


oo 


14 


35 


i 

01*01 1 WiFH REFLECTOR 


4-OtoS-Odb 


O 


35 


70 


MH 

■ 

i 

AR3AV 


7-Oto8-Odh 


Q 


35 + 




70 + 



With tho " Antex " design, the aerial rods radiate in this form 
from a single junction unit. Ono pair of rods constitutes a V 
dipole ; the other pair, forming a V on the same plane, acts as a 
modified director. Maximum signal pick-up is obtained when the 
directors are pointed towards the transmitter. The manufac- 
turers (Antifercnco Ltd.) claim that this aerial has a hotter per- 
formance than tho H type, with less susceptibility to ignition- 
interference signals arriving from below the horizontal, and that 
it is oasier to install. 

Another variation is tho Band I " Bi-Squnre aerial intended 
primarily for long range loft installations as the overall size is 
of tho order of 5$ ft. square. Tho manufacturers (Labgear Ltd) 
claim that good results can usually be achiovod up to 40-50 
miles from a main transmitter. 



134 



TELEVISION ENGINEERS' POCKET BOOK 



Folded Dipole 

Tn this arrangement two half- wave aerials are connected at 
the ends and run parallel to one another, some | in. or so apart, 
one dipole being broken at the centre for connection to tho 
transmission line. Tho polar diagram and gain are substantially 
the same as for a simple dipole, but tho system has a broader 
band -width, while the impedance is approximately four times 
greater. These characteristics are of value for multi-element 
arrays in order to simplify matching to the feeder. 

Multi-element Arrays 

This typo is intended mainly or use in fringe areas. It 
possesses a very high order of gain and directivity, together with 
a slightly reduced hand-width, both ef which improve the signal- 
to-noise ratio. The forward gain is about 8 db, and the front-to- 
hack ratio about 20 dh. The array is usually composed of one or 
more director elements, a dipole and a reflector. 

Room Aerials 

One result of the greater BBOBli ivity of modern receivers is 1 1 mi 
telescopic and other simple room aerials are capable of providing 
reasonable results over quite large areas, although —particularly 
Oil Band 111 pockets of poor signal strength are likely to be 
found even close to tin- transmit tors. Many of these aerials arc 
basically Band III di poles which also provide a roughh equiva- 
lent signal from Band I stations whoso signal strength's tend to 
be higher. 

The hest location for these aerials can bo found only by trial 
and error; moving the aerial to find a place when"- there is 
m i nimum fading caused by people moving in the room (or 

beyond a party wall i and freedom from " ghosf " images. 

Loft Aerials 

Special loft aerials are available which have directional pro- 
perties. An example is tho inverted V type, which possesses 
sharp minima at right angles to its plane, an advantage for the 
removal of '-ghosts" or the elimination of local interference. 
It comprises two quarter- wave rods set at 45° to tho vertical, 
each half of the V being connected to the feeder cable, thus 
making it independent of the auglo of polarisation. 

High-gain " bi-square " loft aerials (Labgear Ltd.) arc also 
available for long-distance reeept ion on Band 1 for use in locations 
where outdoor aerials woidd be difficult to erect. 

Slot Aerials 

This type of aerial may be used as an alternative to the simple 
dipole, or dipole and reflector, to which is has roughly similar 
performance. For installation in the loft of a house, it has 
tho advantage that, for vertically polarised transmissions, it is 






RECEIVER AERIALS 



135 






long rather than high. It consists of a vertical sheet of con- 
ducting material, such as wire netting, with a slot running 
horizontally in the centre and tho feeder connected to the mid- 
points of the long sides of the slot. Typical dimensions for 
Channel 1 are : netting, la ft. long x 6 ft. high (these dimensions 
are not critical) ; slot 10 ft. long x 1 ft. high. 

Skeleton Slot Aerials 

A form of tho slot aerial that is in common use for Band 1 1 1 
reception is the " skeleton slot ". As its name implies, this type 
of aerial was developed from tho normal slot, by gradually reducing 
the metal sm round. 1 1 has been found that results substantially 
i he same as those of the normal slot may be obtained even when 
the surround is reduced to a mere rim of metal, which in practice 
may lake the form of metal tubing (about i in. diameter) enclosing 
tho "slot". This provides an aerial which is comparatively 
simple mechanically, and which does not offer the wind resistance 
ol' conventional slot assemblies. Directive arrays may be formed 
by adding directors or reflectors, though these will be mounted 
at 1)0° to the major axis of the slot. Tho feeder is norma 1 1> 
matched to the mid-points of the slot (where the impedance may 
ho as high as 600 ohms) by means of a quarter wave stub or a 
linear transformer section. 



A K RIALS FOB BAND HI 

On the higher frequencies of Band Ml the voltage induced in 
a dipole element is appreciably less than t hat induced in a Band I 
dipole in an area Ol similar signal strength, while the losses in 
feeder cables will be approximately doubled; furthermore, the 

u-at ivity of a receiver will not be so good on Band III as on 
Band I. For nl reasons, greater care lias to he taken i( 

L'ood signals are to be presented to the recoiver on Band III, 
On the credit side, however, the shorter olements make multi- 
element arrays relatively simple to construct and, in fact, 
arrays of ten 'or so elements mounted on a single cross-arm are 
available. These are highly direct ional. and great, care should he 
taken to orientate them correctly in order to obtain the optimum 
results. 

When planning aerial installations for both bands, the follow- 
ing questions need to be answered before any decision can be 
made as to the best type for a given location: 

(1) Are tho transmitters co-sited or located in different direc- 
tions from the receiver? 

(2) Is tho location within the primary service area (i.e., high 
signal strengths) of one or both stations? 

(3) Is a Band I aerial already installed? This may enable a 
Band III aerial adaptor kit. as available from most aerial manu- 
facturers, to be used. 



136 



TELEVISION ENGINEERS' POCKET BOOK 






(4) Is tho feeder run comparatively short {not more than abt ml 
50 ft.), or will u long cablo run bo required? Loss of signal in 
short runs is usually unimportant, but this will not be tho case 
with long runs on Band III. 

Undoubtedly, ono of the major sources of difficulty with Band 
III aerials is the greater number of " ghost " images that occur 
on these transmissions. Hills, gasholders, spires, steel structures 
and many other reflecting surfaces may give rise to strong 
signals, arriving slightly out of phase with the direct signals, 
and thus producing ghost images slightly displaced from the 
main ones. These can often bo eliminated by very careful 
orientation of the aerial, sometimes suffering some reduction in 
strength of the main signal. 

On Band III, poor aerial siting or installation can seriously 
impair picture quality ovon within a comparatively short distance 
from the transmitter. Manufacturers have drawn attention to 
i In- advantages of an aerial sil'ed above the chimney stack and as 
far us possible from obstructions; or failing this erected so that 
the chimney is to the side of, or behind, the aerial. Loft aerials 
for Band III are often rendered useless by tho proximity of the 
water tank. 

The following are among the suggestions put forward bj B 
prominent manufacturer: 

Install an outdoor aerial. 

Have it on a high chimney. 

Use a good -quality low- loss feeder cable. 

Use the sensitivity control on the receiver to obtain a good 
picture on tho weaker signal. 

Use an attenuator on tho stronger signal to equate the i wo 
signals. 

Remember that multi-clemont aerials are very directional, 
and even a few degrees off beam will make a big difference. 

Band I/Band III Tuned Filters 

Filter units for separating or combining Band I and Band III 
signals — known variously as " cross-over filters ", " diplexers ", 
" splitters ", etc, — have a number of uses. For example, such a 
unit is necessary whore separate Band I and Band III aerials aro 
used with a receiver having a single input socket, or alternatively 
whero a combined Band I/Band III aerial is used with a receiver 
having separata input sockets. Two filter units may be useful 
whore separate aerials and separate input sockets exist in those 
locations requiring long low-attonuation feoder cables; in these 
circumstances the cost, of two filter units may be less than that of 
the length of cable which is rendered unnecessary by tho use of 
one filter mounted close to the aerials and a second filter at the 
receiver end of the feeder cable. 

FEEDERS 
At radio froquoncios a length of feeder cable may bo considered 
as a series of resonant tuned circuits. By variations in ratio 



RECEIVER AERIALS 137 

Table 10.3.-— Typical Attenuation Losses in Fkkokrs 



Type of Cable 


Attenuation tern 
(dbfLOofl.) 
! mi i<f<lance 


(OAfns) 

60 Mel* 


200 J/e/a 


Solid polythene co-asinl 
i.'ullular polythene co-axial 
SamtaiMgttoed co-uxinl 


75 2-9 
75 2-3 
75 1-6 


6-4 
4-0 
3-5 



of inner to outer conductor and conductor spacing, cables having 
wide limits of characteristic impedance are possible. 

Whilst the terminating impedance of a television dipolc aerial 
is about 72 ohms, that of a multi -element array for use in fringe 
areas, etc., may be as low as Ifl ohms, and is frequently about 
40 ohms. The matching of a suitable feeder is thus a matter of 
considerable importance. 

In tho case of unscreened twin cables, tho impedanco and 
attenuation characteristics are quoted for a cable length in free 
air, and thus tho proximity of metallic objects must be considered 
when carrying out an installation. Adverse effects are negligible 
with 72-ohm twin, but very important with higher impedance. 

Tho semi -air-spaced typo of cable provides a useful low-loss 
co-axial feeder. Unfortunately it cannot be extended to small 
balanced screened cables because of physical limitations. 

Absorption Trap 

This device consists of an electrical quartor-wavolength of 
feeder cable similar to that used for the aerial downlead, the outer 
conductor of which is connected to the outer conductor of tho 
aerial feeder at I In: receiver end; tho two inner OOndoCtOTB an- 
also joined together. It is of great value where sound trans- 
mitters cause interference. 

The length of the quarter-wavelength cablo should be reduced 
by cutting its free end until the interference is eliminated. 

The Use of Cables as Transformers 

Although a stub-matching device to correct impedance is 
usually provided, instances may arise whero tho installation 
engineer has to provide a matching transformer. A quarter- 



L... 



BALANCED 



rOUTER SCREEN 

;,„ ■ i 



UNBALANCED 



U— 4— J 



SCREEN OF 
CO-AXIAL LINE 



CENTRE 

CONDUCTOR 



FW. |..c-Ttim.h; L'o-AXl4J. OjJK-TO-OjiR TjiANSt'OHHKH. 



138 TELEVISION ENGINEERS' POCKET BOOK 

BALANCED 



r 



us 



UNBALANCED 
DUMMY CO-AXIAL 



fk;. 2. -Kummvma tttk of quahtkr-ivavr 'riuNsi'-oiisiKit. 



wavelength of double-screened cable, connected as in Fig. I, 
gives a I : 1 transformer between balanced and unbalanced lines, 
The quarter-wavelength refers to the co-uxial formed by the two 
screens: the insulation between which should be nolvthene rather 
than P.V.C. 

Alternatively, the method shown in Fig. 2 may he used; it 
uses an extra quarter-wavelength of the coaxial line. The 
quarter-wavelength refers to the balanced line formed by the 
two screens of the co-axiuls, the velocity of tins lino being con- 
trolled by the composite dielectric of sheaths and air between tho 
two screens. The balanced load is connected between tho 
screens of the main and dummy co-axials, the lattor being 
connected to the inner of tho main eo-axial, and also short- 
circuited to the screen of the main co-axial at ti distance of a 
quarter-wavelength from the junction. 

The use of a half- wavelength cable provides a 4 : 1 transformer, 
and is useful for connecting a high-impedance balanced land 
(fj/.. a folded dipolc or open wire feeder) to a co-axial, see Fig. 3. 
The boner conductor of the eo-axial is connected to one side of t he 
l»a lanced load and to a farther half-wavelength of similar eo 
axial. Tin- inner conductor of this short length is connected at 

the i'nr end to the other side of the balanced load. 

Matching Television Aerials to Feeder Cables 

The addition of parasitic elements reduces the impedance at 
the centre of a half- wave dipole. This mis-match which oecurs 
when an H type aerial is connected to, say, an S()-ohm cable 
is generally regarded as insignificant, but with multi-element 
arrays some means must lie found of overcoming this difficulty. 

Two popular methods of raising the effective impedance are : 
(1) by the use of folded dipoles, and (2) by the insertion of a 
quarter- wave transformer. 



L... 



BALANCED 




£ LOOP 



UNBALANCED 



FlC. ?,. FOIUI-TO-CJXE TUAXSFOEIMKR 



RECEIVER AERIALS 



139 



The folded-dipolc consists of two or more half-wave aerials 
with their ends connected together, running parallel and closely 
spaced to ono another, wiih the feeder cable connected to the 
centre of only one nI the el. •incuts. With two similar elements 
such an arrangement, provides an impedance step-up of 4 to J, 
and three elements 9 to I. A wide range of step -up ratios can 
be obtained by using elements of dissimilar -diameter tubing. . 

The quarter-wave transformer consists of the appropriate 
length of transmission line inserted between the aerial and tho 
feeder cable. The characteristic impedance of the transformer is 
given by the formula : 

z, = Vz\ x z % 

where Z t is the characteristic impedance of transformer; 

Z 1 is the c characteristic impedance of tho feeder cable ; 
Z 2 is the impedance of the aerial. 

Two other methods occasionally used are: (1) to make use 
of the relatively high impedance at the end of the dipole, and 
(2) by T matching the cable to the aerial element. In the case 
of (1), which is practical only with arrays using four or moro 
elements, a step-down quarter- wave matching stub is usually 
required. With (2) the feeder wires are connected not to the 
centre of tho dipole but to points a few inches above and below 
tho centre. Both of theso methods are inclined to reduce the 
baud-width and to make the dimensions rather critical. 



ATTENUATORS 

The two types commonly used are the "pi" and the " T ". 
The " pi " is more suitable for test purposes, as it uses higher 
resistance values. Fig. 4 (a) shows tho circuit, and resistance 
values for different attenuation requirements are Riven in Table 
10.4. 

Table 10.4 



Required A pproiima tt 
Attenuation, db 



10 
SO 
30 

41- 

50 



JO, Ohms 



83, Ohms 



150 
-170 

1,500 
K.'IIHI 

10,000 

::.'.■ on 



100 
100 
82 
82 
82 
82 



llcsistore should be of J-W normal rating, with tolerance o( ±10 per cent, non- 
iii-hiiHivc. 

The " T " typo circuit is shown in Fig. 4 (6). Above 20 db 
attenuation this type is not suitable, as the resistance value of 



140 



O — 



TELEVISION ENGINEERS' POCKET BOOK 



Rl 



Rl 
O— wVWV- 



Rl 
-WWV O 



■R2 



'R2 



•R2 



(a) 



Rl 
O— \AAAA/- 



Rl 

-wwv c- 



(b) 



Rl 






:R2 



:R2 



:r? 



Rl 
0— \AAAAr 



Rl 
^AAA/V— <■ 



(O 



Rl 

-\AAMr- 



(d) 



Required Apjrmximatc t r . nh ,,„ n . 
Alternation, ill, R\,0hms R2,0hms 


10 

20 


39 
63 


66 

16 



RECEIVER AERIALS 



141 



Fir.. 4,— Attenuators : («) "pi" TYTE; (ft) "T" Tyi>k; (c> " T " TYPE TOR 

BALANCKU "J'VVIS- PSKDBHH; (d) " \n " Tll-E FOR JJALANCKI) TWO FKBDEBS, 

R2 becomes too small. Resistance values are given in Table 
10.5. 

Table iO.S 



The circuits given aro for use with co-axial feeders. Where 
balanced twin feeders are used the valuo of Rl should be halved 
and the circuits are as shown in Fig. 4 (c) and (d). 

AERIAL INSTALLATION 

The recognised method of attaching an aerial to a chimney 
stock is by the use of a right-angle bracket engaging on a corner 
of i ho stack and tensionod against it by a wire lashing located 
around the stack. The object is twofold. Firstly, it avoids 
hammering holes in (he brickwork and thus weakening the stack, 
particularly in the ease of old property. Secondly, it avoids the 
legal impli cations of landlord's fixtures, and the aerial may thoro- 
i'ore bo Subsequently removed by an outgoing tenant if lie is tho 
owner. Brackets aw usually cast in high-tensile aluminium 
alloys to avoid the need for protective finishes. 

Suitable lashing wire is galvanised 7/10 s.w.g, high-tensile 
steel wire, the tensioning being taken up by J bolts, which are 
located on the corner bracket and are hooked into ferrules spliced 



<(ii to the lashing wire. To avoid chafing, tho lashing wire passes 
. >\cr small angle brackets located at tho three remaining corners 
of the stack, held in tension by the lashing wire. Single-flue 
chimneys are generally considered unsatisfactory for Band I 
.serials; two-flue chimneys are suitable for most normal in- 
-i illations, but four-flue chimneys should be used for heavy 
multi -element arrays unless the mast is " stayed ". Wherever 
possible the aerial elements should be kept clear of the chimney 
outlet to avoid damage when the chimney is swept and deteriora- 
tion duo to smoke contamination. 

Feeder cables tend to deteriorate rapidly where long stretches, 
cither vertical or horizontal, are left without proper anchoring 
and are thus subject to continuous strain from their own weight 
or to grazing by wind action. Where cables eomo down over 
tiled roofs suitable tilo clips, such as Francis wall nails, should be 
used to anchor the cablo by careful insertion under the tiles. 
Preferably the cable should bo fastened at intervals not greater 
than 3 ft. for vertical runs and 1 ft. for horizontal runs. Where 
soft lead or other metal nails or electricians' cleats are usod to 
secure the feeder to roofs and outer walls, a small piece of fibre 
or tape should be wrapped around the cable to prevent tho fixing 
metal from puncturing tho outer sheathing. The fixing cleat 
-limitd nut l>i- hammered home too hard, ulhcnvisc (lie ''aide will 
be subject to excessive pinching and I lie sheathing may bo 
punctured, allowing moisture to enter, with consequent loss of 
signals. The feeder should be looped slightly away from any 
woodwork so as not to interfere with painting. Whore the 
feeder is routed externally to the mast it should be taped to the 
mast using water-proof tape, it should bo taken behind gutter- 
ing and on to the gutter board or alternatively stand -off brackets 
should be used. 

At the point where the feeder enters the building a water-drip 
loop should be formed in the feeder and entry holes should be 
drilled at an angle of 4;> degreos downwards from tho inside. 

No matter how good the aerial installation, considerable 

deterioration takes place under continuous exposure to a smoky 

atmosphere and variable weather. Therefore to maintain its 

ilteiouey, regular inspection and repainting should take place, 

preferably at intervals not exceeding two years. 

Multi-receiver Installations 

Where there is only one convenient mounting point for two 
houses or flats, it is often more satisfactory to feed two receivers 
from a single aerial rather than to place two aerials in close 
proximity. This can be done without difficulty, provided that 
the signal strength in the area, for tho type of aerial system 
employed, is sufficient to permit a loss of db from the signal 
which would be fed to a single receiver. Htar networks which 
enable two receivers to be fed from a single co -axial or twin- 
feeder line are shown in Fig. 5. 



M2 



TELEVISION ENGINEERS' POCKET BOOK 






RECflVER'A"-^ 




REC£lveR"B"~ 




RECEIVER "8" 



(a) (b) 

Km. *). — STAit NSTW0BK8: (,aj OO-AXIAI PBBDEB; (6) Twin L-'kkiieh. 

Where it is desired to operate a large number of receivers 
from ono aerial without, loss of signal, as may be the case in a 
service workshop, a block of flats or a hotel, it is essential to 
ensure that there is no interaction between receivers, and that 
all outlets receive a satisfactory signal. This will normally 
entail the use of a distribution amplifier in conjunction with an 
efficient aerial, suitable eablo runs and correct socket outlets. 
The distribution ampltfior should be fitted as near to the aerial 
as possible, and suitably accommodated in a dry. weatherproof 
room or enclosure, properly ventilated and reasonably free from 
dust. Flue gases or smoke should not bo allowed to cuter the 
amplifier enclosure, us otherwise rapid corrosion of mctahvork 
may be experienced. Where exceptionally long cable runs aru 
necessary, it may be advisable to use air-spaced co-axial cable. 

Fringe-area Equipment 

Since valve noiso becomes increasingly important as the input 
to the first R.F. stage falls, losses in the feeder line are often the 
decisive factor in determining whether or not a satisfactory 
picture can be obtained in a fringe area. Special low-loss air- 
spaced cables are available for fringe area installations. 

Since special feeder cables are considerably more expensive 
than the standard types, it will be necessary, in many border- 
line cases, to weigh carefully the relative costs of the various 
types of aerial arrays, high masts, preamplifiers, cable.** and the 
like. For example, it may be found more economical to use a 
more complicated array with standard cable than a simple aerial 
with special cable, or vice versa. 

" Ghost Images " 

Reflection of signals from natural and man-made objects may 
cause a double uv multiple image ii> appear upon the screen of a 
receiver; and in certain districts sttoh conditions may prove 
most troublesome and difficult to overcome. Hill faces arc 
probably the most frequent cause of " echo " signals, but almost 
any reflective surface, such as trees, buildings, gasometers, or 
factory chimneys, may give rise to " ghosts ". By measuring the 
displacement of the spurious image, a rough estimate may be made 
of the distance of the offending objects. 






. 



RECEIVER AERIALS 



143 



ACTUAL iWGHOST £bHC$T 
OUTLINE OUTLINE OUTLINE 





W 



VlC. 8. — GHOST LMACES. 



{>>) 



The approximate image-displacement values ami distances of 
the reflecting structure; from the aerial for a 15-in. cathode-ray 
tube are given in Table 10.0. 

Intermediate angles between the rear and side-on positions 
will give intermediate values between those shown in (he middle 
and right-hand columns. Objects slightly in front- of the side- 
fa) view would he at a distance greater than that given by the 
middle column. 

The cure of double images is still largely a- ma Iter of trial and 
error in the positioning and orientation of the aerial : the prin- 
ciple being the adjustment of the system to givo minimum 
pick-up of the '"ghost" reflection. It is, for example, useless 
in areas prone to "ghosts" merely to point ihe aerial towards 
the transmitter. Instead, the aerial should be carefully adjusted 
when a programme, preferably Test Card " C ", is being received. 

Table 10.6 



Di.t/itaMHtnt 


<>( 


Object to Right 


Qttftei /mimdi'i irl u 


Imag? 




or Left 


Btktod 


tV iu. 




1 ID yiirtls 


70 vnrda 


JL 




we „ 


95 „ 


A .. 




380 „ 


11a 


1 » 




2S0 „ 


lla ,. 


!: 




see ,. 


B80 




1J miles 


linn .. 


2 „ 




21 „ 


1J miles 



fii some cases it may prove easier to reject tho direct signal and 
concentrate on receiving the reflected signal, for example by 
turning tho aerial on its side so as to receive horizontally rather 
than vertically polarised waves. With indoor aerials, a change of 
position of only a foot or two may make a considerable difference 
to results. 



[SECTION 11] 
INTERFERENCE 

The very high frequencies (30-300 Mc/s) on which television 
broadcasting at present takes place, are part iculnrly susceptible 
to interference from local electrical appliances and spark -ignition 
systems, the interfering signals arriving at the receiver either by 
direct radiation from the source or by conducted radiation along 
power mains and overhead wiring, or by a combination of the 
two. 

The Engineering Branch of the G.P.O is prepared to assist 
liconce holders in the tracing of man-made interference and to 
offer advico on its suppression. Applications for assistance, 
which is provided free of charge, should bo made by liconce 
holders on Form T.466G " Electrical Interference Questionnaire ", 
obtain ablo from any Head Post Office. 

It is, however, of considerable importance that the installation 
and servicing engineer should be able to distinguish between 
local interference and receiver faults, to recognise tho various 
types of interference from the symptoms they produce upon tho 
picture and to know what can he achieved by the installation of 
suppression devices to minimise the effects of such interference. 

In practice, interfering signals fall into two main categories, 
which require entirely different treatment : the impulse type of 
interference producing spots or lines of peak white across the 
screen, and continuous wave signals on frequencies falling within 
the acceptance band of the receiver and producing heterodyne 
interference in tho form of a "herring-bono " pattern of alternate 
dark and light bands miming diagonally across the screen. 



Impulse Interference 

Electrical apparatus which utilises commutation {e.g., D.C. 
motors and generators), vibrating contact points (e.g., electric 
shavers), spark discharge [e.g., automobile ignition) or any 
mochanism whereby an eloctric spark, however minute, is pro- 
duced will radiate R.F. waves, covoring a wide frequency spectrum, 
unless preventive measures are taken. Such signals will cause 
crackling on sound and a series of white spots or bright streaks 
of light on tho screen. In this category must also bo included 
switching circuits, such as thermostats and dirty light switches, 
where slight arcing may take place. As with all forms of inter- 
ference, the effect will largely depend upon the ratio of tho lovels 
of the interfering signal to the picture signal, and will thus be 
more severe in " fringe " areas. 

144 






INTERFERENCE 



145 






By far tho most satisfactory cure is tho suppression of such 
Interference at tho source : ignition interference, for example, 
cjui be greatly reduced by the fitting of a resistor of about 15,000 
ohms in the lead from the distributor to the induction eoil or 
magneto; while most small electric motors as fitted to domestic 
appliances will respond satisfactorily to the fitting of a capacitor, 
or capacitor-choke filter, which will provide an alternative path 
for the K.F, pulses, and which should bo positioned close to tbo 
offending apparatus. Aii increasing proportion of home appliances 
include built-in suppressors, but for other apparatus a wide range 
of proprietary filters are now manufactured; typical circuits 
arc shown in Fig. 1. 



"dj- 1 t 



r x - u 



(at 



lb) 



VHFC 



AlOpF 



r~x 



J5 *Wp 

e — 1 — TJJiJ( 



MP— ° 

VHFC 



VHFC 



<c> 



VHFG 

ITOp' 



f ^ ^" c 



— rSGHSP — a 

VHFC 



<70pFj 
VHFC 



<d> 



RFC 

-TiBTRffi^— o 



RFC 



<e» 



(ft 



(ql 



VU1. !.— BASK! iBHBlFKItKXlIL SlTJ'llKSSTu.N' HKV1CKS. 



(a) For two-core cahlc appliances. V>) For three-t:ore calue appliances, (e) For 
luree-pin socket, (d) Vox HteranoBtot*. Types (c) and CO are for tlie suppression of 
tele vision interference from two- and three-core appliances. (.0) All-wave tilter for 
i i ■ i:n If.-i-rt ami television interference suppression. The value of U may vary hetweeu 
■i-hiI and u-o nV. Values given for type (c) arc the largest peonWue. 

Where the source is unknown or cannot readily be suppressed. 
tho effects can bo reduced by : (1) the provision, on the sound 
and vision receiver units, of interference limitcr circuits, designed 
to cut off tho high amplitude peaks of tho interfering signals- 
popular circuits for such lim iters are shown in Fig. 2 («)-{/i) (in 
practice the valve diodes are sometimes replaced by germanium 
crystal diodes) — or alternatively, by inverting the pulses so that 
they produce black instead of white spots (see pages 45-46) ; (2) 
ensuring that the most efficient aerial system is employed, with 
the elements as far away as possible from the source of inter- 
ference or from wires and guttering that could form conduction 
paths; (3) where the source of the interference is known, as, for 
example, the ears passing along a main road, a directional 
aerial system may be orientated so as to provide minimum 
pick-up from this direction; (4) the use of interference filters in 
the mains supply loads to the receiver. Method (4) is unlikely 



146 



TELEVISION ENGINEERS' POCKET BOOK 



to prove as effective at television frequencies as for normal 
broadcasting frequencies owing to the greater ease will, which 
the leads beforo and after the filter can" act as aerials and thus 
allow the interference to bridge the filter; nevertheless, a number 
or filters especially designed for use at television frequencies 
are now on the market, and will often bring about a considerable 
improvement, particularly when used in conjunction with 
methods (1) (3). 

An effect somewhat akin to ignition interference may be caused 




KIG. 3,—lBtOTWBRKSeB-fflJPRHaBSKttJ Cmc'UITS. 

(a) Basic viM.,M-intrTi,.rei).'.! npptea&n! fin-Nit.. (I,) Automatic form of peak 
limner, (c) Ijpicul pnke-wf&tl Jimitcr eir.-uit. (,/> Visi.m-interfereiioe limiter 
operating on a. time- cons runt, basis. 

by corona discharge (" brushing ") from points at E.H.T. potential, 

hut it can easily be recognised by its more continuous naturo. 

Heterodyne Interference 

The second and loss common group of interfering signals are 
those in which oscillation is continuous, as opposed to trains of 
damped oscillation, and these are usually tunable over a com- 
paratively narrow band; they produce heterodyne interference 
against which peak limiters and suppression filters of the typo so 
far described are ineffective. The most common causes of such 
interference are diathermy apparatus, adjacent-channel inter. 
ferenee, harmonics of short-wave broadcasting, communication 
and amateur transmitters, and radiation from the local oscillator 
ol other television or short-wave receivers. Susceptibility to 
certain forms of this interference particularly, for example 



INTERFERENCE 



147 



to break-through on 
l he intermediate fre- 
quency of the tele- 
vision receiver, will 

depend very largely 
upon the inherent de- 
sign of the receiver and 
the choice of the inter- 
mediate frequency. 

The interference 
may arise from radia- 
tion (usually harmonic) 
taking place at fre- 
quencies within or 
close to the television 
channel (in this case 





PM. 4.— TSTTllPlcnEXrr: CAUSED iiv RtECTBH 

Morons, 



through of a signal on 
a frequency close to 
the intermediate fre- 
quency; or from a 
combination of these. 
By fitting suitable 
traps and filters in the 
offending transmil ler. 
and by careful screen- 
ing, harmonic radia- 
tion can be much 
reduced. Rejection of 
fundamental or inter- 
mediate frequency --'n.'- 
nals can often be im- 
proved by sen 



Fro. S. — i Karoos Tntrrveiuskck. 

suppression at the 
sourcei ir careful oriel il - 
alien of tho receiving 
aerial are likely to 
be the only effective 
cures); to image 
(second channel) re- 
sponse in Uie receiver j 
from " blanketing''' or 
swamping of tho re- 
ceiver by very strong 
local signals, or cross 
modulation, some - 
times produced by rec- 
f ification in the aerial 
system or local metal- 
work : from break- 







FIC. 5. — MODUI-ATKh U.K. ISTERFEriFSOF.. 



148 



TELEVISION ENGINEERS' POCKET BOOK 



traps or filters in the aerial feeder of tho receiver, close to 
i In- receiver, or alternatively as elose as possible to the control 
grid of the first R.F. amplifier or mixer valvo. Such a wave 
trap resembles those used in the early days of broadcasting, 
and is tuned to the unwanted frequency (provided that this does 
not lie within the required television channel). A coil with 
10 turns of 18 S.W.G. wire, spaced wire diameter, and with an 
internal diameter of -ft in.', tuned by a 3-30- pF brimmer, will 
have a tuning range of about 40-50 Mc/s, and for offending 
signals on other frequencies tliu number of turns should be 
increased or decreased accordingly. For tho rejection of signals 
at intermediate frequencies, high-pass filters with a pass band of 
about 40-60 Mc/s may bo fitted in the aerial lead of tho receiver, 
and will normally prove effective provided that the screening of 
the I.F. stages is adequate to prevent direct picU-up. Here 
again, careful positioning and orientation of aerials may prove 
of assistance. 




l-'tli. 0, -SKVBllK DtATUIfKMY 
DrnSBFHBMHOB. 



Diathermy 

This is a particular form of heterodyne interference, the cause 
in this case being the harmonic output from tho relatively 
unsmoothed valve oscillators used in electro-medical apparatus. 
In addition to the herring-bone pattern, tho sound channel is 
often affected by harsh crackling or low-pitched hum. Tho 
most satisfactory cure for this form of interference is the complete 
electrical screening of tho offending apparatus; though in some 
cases relief can be obtained by slightly changing tho frequency 
ot oscillation of tho equipment so that the harmonic's no longer 
tall m the television channel concerned. 

Freak Propagation 

Owing to tho fact that television channels are shared on a 
geographical basis, herring-bone interference patterns may 
sometimes be caused by signals being received from a distant 









INTERFERENCE 



149 



station, normally inaudible. The most common cause of such 
n propagatiounl condition is a period of "Sporadic E ", when 
the E layer becomes highly ionised and reflects signals up to 
about 70 -Mc/s over distances between 201) and 1,000 miles. 
Pronounced temperature inversions, such as occur during 
summer evenings, may also cause slight, interference. As such 
conditions seldom last for long, it is usually considered mi- 
necessary to take precautions against this form of interference. 



Aircraft Flutter 

Reflection of signals from aircraft may provide alternate 
augmentation and attenuation of the signal as the phase of the 
reflected signal changes in relation to that of tho direct signal; 
this will cause tho contrast of the picture to change rapidly 
from normal to low and then to high, the cycle being re- 
peated in rapid succession for us long as the aircraft is in the 
neighbourhood. 

The degree to which a particular receiver installation is sus- 
ceptible to this form of interference will largely depend upon the 
aerial system : a system which receives only vertically polarised 
signals will generally he less affected than one capable of re- 
sponding to i he horizontal component. The effects may also bo 
diminished l>y reducing I he l).(.\ coupling to the cathode-ray 
tube, or by the use of some form of automatic picture control. 

Interference hy Television Receivers 

Radiation of parasitic oscillation occurring in a television 
receiver may affect local broad easting and television receivers: 
the cure hero is to find tho source of tho parasitic oscillation and 
to improve the stability of the offending stage(s). 

Radiation in the form of induced electric and magnetic fields 
may be set up in the neighbourhood of a television receiver, and 
may affect nearby broadcasting receivers, particularly on the 
long-wave band. *Tho most likely sources of these fields arc tho 
line-output transformer and associated points at K.H.T., tho 
deflector coils and the high- impedance circuits near thoso com- 
ponents. Tho following methods of reducing such interference 
have been recommended by Messrs. Mullard, Ltd. : 

(1) Tho E.H.T. transformer, booster diodo and line-output 
valvo should bo totally screened by a can which makes good 
contact with tho chassis. Two -hole fixing of the can is not 
entirely satisfactory, and it is advisable to make multiple con- 
nections betweon can and chassis. _ The difference in radiation 
between a good and a bad connection hero may amount to as 
much as 8 db for magnetic fields. 

(2) Any width or linearity controls of the inductor type 
should be screened .separately if they cannot bo accommodated 
insido the line-output screening can. (Tho design of the line. 



ISO 



TELEVISION ENGINEERS' POCKET BOOK 



Tabus 11,1. — Causes op Television Interference Investi- 
gated by tub C.P.O. nuitrera a Tyimcai. Twelve-moot* 

Period 



Caiisr 


Number 


Unknown : not observed by P.O. stall 
Sewing-mac bine motors 
Faulty receivers .... 
Hair-dryers .... 
Incllicieitti aerial-ear ill systems 

Motors, rafooeUuBOOOB . 

Drills 

Vacuum clamors .... 
Lamps (Nlameiu type) 

Refrigerators .... 
Bed-warmers .... 
Thermostats, miscellaneous . 
ltndio transmitters 

Radiation from superset local oscillator 
Neon-sign tubes .... 
Uadical apparstus (valre) 
Mis-operation of receivers 

Fault; wiring of bnfldiogs 

Electric toys ..... 
Dental motors ..... 

Hells 

Floomtcaat tubes ..... 
llnlary converters . 






1.1,072 
9,936 

4,37a 

1.155 
1,827 

I.7 7S 

1.CI7 

1,621 

1,132 

1,193 

1,009 

1,088 

937 

7(56 

755 

G98 

050 

GIG 

•139 

■110 

361 

301 

-281 

364 

34 1 

17G 

161 



output scrconing involves problems of ventilation to avoid 
overheating of the components enclosed by the screen. (As a 
general guide, the maximum safe bulb temperature for tho PL8I 

line-output pentode lias been determined at 1S.V (Vol tirade.) 

(3) The deflector coils should bo screened as far as possible 
by an aluminium can or by metal foil wound co-axially around the 
coil and earl lied to chassis. Care must be taken to ensure that 
there is no likelihood of voltage breakdown between tho foil and 
the coils. This form of screening will give good reduction of 
electric fields, and will also reduce magnetic fields, though not 
to the same degree. To reduce the magnetic field still further, 
the deflector coil-serecning can should havo endplates with holes 
only just large enough for the tube neck to pass through. This 
gives a further reduction of approximately 6 db. 

(4) Care should be taken in the layout of the receiver to keep 
circuits of high impedance well away from the worst sources of 
interference. 

(5) Tho graphite coating of tho cathode-ray tubo should be 
efficiently connected to earth -preferably from two separate 
points on the coating. 






INTERFERENCE 



151 



(6) Both conductors of the mains supply should bo connected 
to tho earth terminal via 0-05-uF paper capacitors rated for 
COO V (r.m.s.) working. 

(7) The uso of a perforated foil screen at tho back of the set 
will reduce radiation in that direction. 

As already mentioned, interference with radio reception can be 
due to both electro-static and eloctro-magnetic induced fields : 
the magnetic field will affect only receivers with frame aerials. 
Interference is most commonly caused on the Droitwich long- 
wave programme (l,F>0O m„ 200 kc/s) since the 20th harmonic of 
the television line-scan frequency falls at 202-5 kc/s. 

Where tho interference is not serious enough to warrant altera- 
tions to the receiver, much can bo done to avoid interference on 
a neighbour's radio receiver by carefully selecting the position 
of (ho television receiver. As back radiation is usually the most 
serious, receivers should not bo installed against a party wall 
unless it is known that there is no radio receiver on the other 
side. 

A less frequent cause of interference in radio reception— and 
also in television reception — is parasitic or Barkhausen-Kurz 
oscillations, particularly in tho line-output stage. On the 
television screen such interference may tako the form of irregular 
vertical white lines about 2 in. from the left-hand sido of the 
screen. A cure can often be effected by changing tho line- 
output valve, altering the position of the line-hold control or by 
the use of parasitic suppression dovices. 

A wavering vertical line, similar to that described above and 
often known as " windscreen wiper " interference, is usually due 
to line time-base radiation from a nearby receiver tuned to 
another station. The interference will not be visible if both sets 
are tuned to the same channel, as the radiation occurs mainly 
during the flyback period when the picture is suppressed. 

Patterning interference from Band I receivers converted by 
means of a " univoraal " converter is also fairly common. This 
is discussed in Section 7. 

Where two receivers in close proximity are tuned to different 
transmissions, Bound and or vision interference may arise from 
radiation at th<' common intermediate frequency. This is best 
cured either bv moving one <>f the sets or. if not possible, by fitting 
a high-pass filter in tin- aerial lend of (he affected receiver to pre- 
vent breakthrough of signals at the intermediate frequency. 

Fiys. 3, 4, 5 and 6 are " Teh-Snaps " by John Cura. 



[SECTION 12J 

FAULT FINDING 

by T. B. Smaktt 

The tracing of faults in television, receivers can frequently 
present unexpected difficulties to an engineer who possesses 
impressive theoretical knowledge but who lacks practical experi- 
ence. It is not enough to know how a television set works \ 
unless a thorough basic, knowledge n f radio is supplemented by 
considerable practical experience, vital time will be lost and effort 
misdirected before the cause of a breakdown is finally revealed. 

Preliminary Considerations 

If radio and television repairs are to be carried out on a sound 
economic basis, the engineer must be able to use his past experi- 
ence of the weak points of particular models to enable him to 
locate at onco the cause of the trouble. Often a telephone 
massage IVoin a customer reporting flu- failure will star! fchfl 
engineer thinking of the most probable cause of the breakdown. 
If the message has come via the shop, then the repair slip may 
contain the vital clue. In any event, unless the lengthy process 
of systematic examination can bo ci re um vented in a 'lair pro- 
portion of instai s the repair department will not pay its way. 

The engineer who is most successful in tracing faults'is usually 
the man with n retentive memory and a keen eyo for detail. 
When a chassis lies on the bench 'for examination', the eye and 
sometimes even a keen sense of smell may lead to the cause of the 
trouble before the use of a meter has* been considered. The 
customer often reports M a smell of burning " after switching on. 
The engineer, anxious to save time, will at once watch for a 

cracked or blistered resistor. Once located, the cause of failure; 

sometimes an associated by-pass condenser — can be verified and 
the faulty components replaced. 

Instances of complete breakdown are usually the oasiest 
faults to trace. More difficult are the cases where' the sot works 
but picture quality has deteriorated or is subject to intermittent 
faults which require more lengthy examination. 

For the purpose of fault tracing, the television set may bo 
conveniently divided into sections. In addition, it is very useful 
to have a clear mental picture of the type of waveform normally 
asset-luted with various parts of the circuit, The majority M 
service manuals are very helpful in this respect, as many include 
both waveforms and a voltage analysis taken under stated 
conditions of operation. When dealing with faults in the fcime- 



FAULT FINDING 



153 



base with the aid of an oscilloscope, much time can be saved onco 
the habit of forming a mental picture of the shape and amplitudo 
of the normal trace has been acquired. It is recommended that 
the service engineer should undertake a detailed study of time- 
hascs, as it is in this section of the television set that the most 
frequent failures occur. 

Faults in E.F. Stages 

Faults other than that of valve failure in the R.F. stage are not 
frequently mot. On turning the contrast on full the remainder 
of the set will produce fluctuation noise, which will be apparent 
both from the loudspeaker and the tube raster. The timo-bases 
will bo running freely, and the lower-pitch whistle from the linc- 
outpttt transformer will indicate the lack of synchronising pulses 
from the carrier. Quick verification of the faulty stage can be 
obtained by connecting the aerial to the input grid of the fre- 
quency changer. The tracing of a faulty R.F. stage should pre- 
sent little difficulty, but as the method involved also applies to 
receivers built on tho T.R.F. principle and i.F. amplifier stages, 
the steps to be taken are worthy of some consideration. 

In areas of weak signal strength the aerial should first of all 
be cheeked for a possible short-circuit or open-circuit in the co- 
axial connection to the grid tuning coil. If the fault is at the 
dipole connection, and the centre conductor has become dis- 
connected, some indication of signal can be obtained by making a 
temporary contact between the braiding and the centre connector 
of the co-axial Input socket on tho receiver. If the aerial is in 
order the grid circuit of the first stage should be examined for a 
possible dry joint or opon-circuit. If tho correct D.C. potentials 
are on tho anode and scroen of the valve, the cathodo return 
circuit, should bo checked for an open-circuit. 

Component Deterioration 

Quarter-watt resistors, when of more than 1,000 ohms in value, 
and included in the anodo circuit of an H.F. stage for the purpose 
of de-coupling, can cause trouble by overheating and increasing 
in value. As a rule it is advisable to replace any such components 
by equivalents of half-watt rating. During the course of examina- 
tion of the vision strip it is sometimes very helpful to tap all 
components lightly with an insulated probe. A microphonic 
valve or a condenser with an intermittent fault can often bo 
located by this method. 

Ordinary radio sots are usually quite tolerant of R.F. de- 
coupling condensers that, during the course of years, have 
developed leaks and are in effect resistors. In the ease of 
television receivers, however, the standard of circuit efficiency is 
far more exacting, particularly when tho most has to bo mado of a 
weak signal. When a receiver i\\' the T.R.F. typo has been in 
operation for a number of years, and routine checking of valve 
emission and circuit voltages fails to reveal the cause of low 



154 



TELEVISION ENGINEERS' POCKET BOOK 



O-OSmF 
—IK 







Fig. l.— Typical Early Framf, Time-base. 
In thia clrouft Vlfa) Is used to shape tbe synchronising pulses which trigger the 
blocking oscillator \'Ub); this drives the amplifier V2(ff). The waveforms OMmrriag 
at, points A-I m shown in Fig. 2, and provide a ready means of tracing faults. 

modulation on the cathode-ray tube, it is worth while testing 
for " leaky " components in tho signal-frequency stages. 

R.F. and I.F. Instability and Loss of Signal 

Cases of U.K. or I.V. instability, usually apparent through un- 
controllable peak white modulation on tho tube, ran be traced 
t|uickly by connecting tho grids of the amplifier stages to the 
chassis, starting at the point of the lowest signal. As a rule, i be 
T.R.F. typo of receiver is more inclined to develop this kind of 
trouble than the superhet. A faulty valvo-holder quite often 
proves to be the cause of such instability. If all valve con- 
nections provo to be in order, then the possibility of feedback 
through the wiring of the set should be examined. The position 
of the aerial feeder relative to the final amplifier stage should be 
considered, as feedback is most likely to occur between points of 
high and low signal amplitudes. 

Apart from incorrect alignment, loss of vision signal can some- 
times be duo to incorrect adjustment of rejector circuits. This 
condition is usually indicated by vision-on-sound interference in 
the loudspeaker. The cure is "best effected by re-aligning the 
receiver throughout. In the case of the superhet, lack of signal 
in both vision and sound sections can be due to failure of oscilla- 
i ion in the frequency changer. This is commonly due to either 
loss of emission or a low voltage on the anode of tho oscillator 
valve. Amplifier stages should he checked for o/c. by-pass 
condensers. 






FAULT FINDING 



155 




Fig. 2.— Wavefobmh vrsocutrd with Pte. i. 



Faults in Video-amplifier Stage 

If tho television receiver is considered in two sections, from the 
aerial to tho detector, and from that point to the cathode-ray tube, 
it is in tho second section that the majority of faults are found to 
occur. The video detector itself can cause a fault which may at 
first sight be wrongly attributed to a weak signal from the 
vision strip, or alternatively to a loss of drive from the video 
amplifier. If the detector is of the thermionic type, failure in 
emission will result in a weak picture, loss of synchronisation in 
i In- line and frame lime-bases in short, a numbes of puzzling 
'" red herrings " confront tho fault tracer. It is well to remember 
that crystal detectors are also liable to breakdown. 

The video-amplifier valve handles the rectified signal, and 
should be capable of useful gain over a frequency range extending 
to 3 Mc/s. Tho quality of the television picture depends on the 
efficiency of tho video stage, and on the correct degree of fre- 
quency compensation which is applied to this circuit. In sonic 
vidoo stages the value of the anode load is kept as low as possible. 
If quarter- or half- watt resistors are used in this part of the cirouii , 
and there is evidence of over-heating, it is advisablo to replace 
tho resistors by 2- or 3-W equivalents. Valve efficiency is rather 
critical in the video stage, and any falling off in emission will often 
causo an unsatisfactory- picture, with poor synchronisation if the 
signal strength is low, * 



156 



TELEVISION ENGINEERS* POCKET BOOK 




Fie. 3. — Typical Kaui.y Link XlMB-BASR. 

In tliis circuit, ball iin ROOM la USfti as u blonkinsr uselllntor, tnsRfrp4 til tho line- 
synchronising jiulscs ; the output is llim luunlilied by on Mr.-"; 4 , 'i'iie waveforms 
which occur tit, jiotuts A-E, and which form ;i ready mean of taSH tracing, an: ahowa 
in Vig, 4. 

Faults in Cathode-ray-tube Circuit 

For reasons of economy and efficient circuit design, cathode -ray 
tubcs are cathode driven, and are usually directly coupled to 
the anode of the video amplifier. This connection is sometimes 
made through a resistor of about 100,000 ohms, by -passed at 
video frequencies by a 2-^tF condenser of small siste. The 
network is returned to earth via the high-potential side of the 
brightness control, thereby ensuring that the cathode-ray tube 
grid can never go positive with respoct to the cathode. Some 
components associated with tho cathode circuit of tho tube are 
concerned with the removal of impulsive interference- If this 
circuit fails to operate, the cause will almost certainly be the 
valve, which is biased to conduct on signals above peak white 
modulation level. 

It is sometimes found that a brightness-control potentiometer 
with a worn track can produce a picture fault which may be con- 
fused with the symptoms of failure in the tube-heater-to-cat hade 
insulation. The picture breaks up into strips of varying bright- 
ness, running horizontally, which resemble the blurred areas 
which occur during intermittent heater-to-cathode short-circuits. 

Faults in Synchronising Separator 

When faults occur both in the line- and frame-deflection circuits 
it is logical to trace the cause to a common origin, and the most 
likely component to suspect is the synchronising separator, 
which, owing to loss of emission or faulty resistors in either the 
grid or anode circuit,, may be operating on the wrong part of the 
valve characteristic. If anodo current changes are caused by 
picture content instead of being limited to tho synchronising 






FAULT FINDING 



157 




pulses, then the time- 
liases will run so irregu- 
larly that it may prove 
impossible to lock the 
picture into a steady 
position. The cause of 
troublo in this case will 
often bo traced to the 
0-1 -jtV grid coupling 
condenser to the syn- 
eiironising separator. 
This component should 
have a very low leak- 
age current, and should 
show a resistance of 
about 20 megohms on 
tost. 

Interlacing 

Faulty interlacing of 
the picture-lino struc- 
ture is often duo to 
unwanted coupling be- 
tween tho lino and 
frame oscillators. Al- 
though it is very diffi- 
cult to remove all trace 
of the line-synchronis- 
ing component from the frame pulses, considerable success has 
been achieved in producing well-interlaced pictures in most 
modern receivers. 

Imperfect interlacing produces a serious loss of picturo defini- 
tion in the vertical direction, and may, in extreme cases, produce 
a loss in horizontal definition through the ovcr-lappine; of adja- 
cent lino information. Apart- from the obvious " liny : ' picture 
structure, faulty interlacing can be recognised by a tendency for 
tho start of the half-line trace to wander at the top of the raster. 
This indicates that, the frame time-base is not being triggered at 
the corn -et intervals by the frame-synchronising pulsu. This 
irregularity is due to the variation in the intervals between 
successive fields caused by tho uneven operation of the frame 
time-base. For correct interlacing, the shape and duration of the 
synchronising pulses must not vary. It is through the addition of 
small voltages at line frequency to tho envelope of tho frame pulse 
produced by the integrator circuit that faulty interlacing arises. 
As very small intervals are concerned in producing these wave- 
form irregularities, (he underlying cause is to be found in minor 
circuit variations due to faulty insulation in condensers. Induced 
voltages at line frequency in tho frame- time-base circuits can 
arise from the inadequate screening of tho line-output transformer 
or line-deflection coils. 



Fig, •!.— Wavkkohms asshciateh with Firs. 



158 



TELEVISION ENGINEERS' POCKET BOOK 



Tho cure for some cases of faulty interlacing can only bo 
discovered aftor considerable time lias been spent, using the 
oscilloscope, in the systematic examination of the waveform at 
various points in tho frame-scan circuit. In many modern 
receivers a valve or crystal diode stage separatos tho frame- 
synchronising pulses from tho mixed waveforms in the synchro- 
nising separator. An oscilloscope applied to the anode and 
cathode of the "pulse shapcr" should reveal clean-cut negative- 
going waveforms. 

The presence of pulses at lino frequency can bo revealed in tho 
framo circuit by rendering the frame oscillator inoperative either 
by removing tho valve or disconnecting the H.T. supply. Under 
these conditions the use of the oscilloscope at various points in the 
frame time-base will reveal the extent of the coupling effects 
from the line oscillator. During this experiment both the aerial 
and E.H.T. supply should be disconnected. 

Faults in E.H.T. Circuit 

As the majority of modern receivers obtain their K.H.T. 
supplies from tho rectification of high voltages generated in an 
inductance forming part of the load on the lino-output pentode, 
failures in this part of the set will usually be caused by the strain 
imposod by the high induced voltages. Tho lino-output trans- 
former with tho extra windings to supply tho high-voltago 
rectifier should be a high-grade component throughout, and manu- 
facturers will cut costs hero at their peril ! 

Any partial breakdown in (he insulation of the line-output 
transformer will bo indicated by a characteristic fold-over on 
t he side of the picture. If E.H.T. is also supplied from the winding 
there may be insufficient voltage to produce a picture. The 
faulty component may overheat until a complete winding 
breakdown occurs. The presence of a high potential on tho 
cathode -ray-tu he anode may bo quickly verified by obtaining a 
brush discharge on to Ihe blade of a well-insulated screw-driver. 
Aftor a time the service engineer will become quite expert in 
assessing the E.H.T. voltages by this method. It is wise not to 
apply this test to mains-generated E.H.T. systems, which should 
bo treated with extreme caution at all times. 

Apart from breakdown in the line-output transformer, I ho 
E.H.T. supply may fail through a variety of additional causes, 
and faults in this part of the circuit are very common in some 
receivers. Tho presence of air inside the high-voltage rectifier 
may bo recognised by a purple glow diffused throughout the 
onvelope. If, however, the valve looks in order but still fails to 
develop E.H.T., the cause may be due to u short-circuit in the 
line-output deflection coils, especially if these components have a 
metal shroud. Extensive picture interference is commonly 
caused by corona discharge at high potential points. Carelui 
listening or examination in subdued light will often reveal the 
source of the discharge. Seepage of "E.H.T. across insulated 
surfaces due to dust and dampness can also cause this typo of 






FAULT FINDING 



159 



picture interference. Some manufacturers enclose the entire 
K.H.T. system in a screened compartment, and shorting across 
Hi' the K.H.T. from the cathode oT the diode to the metal case can 
occasionally occur. A slight movement of tho diodo away from 
tho nearest earth potential point will speedily cure this fault, 
1 flack of voltage pulses in the fine-output transformer is indicated 
liy the absence of the characteristic high-pitched whistle, then the 
lack of oscillation can be due to a failure in the line feedback 
circuit, or, possibly, to a faulty oscillator valve or blocking 
oscillator transformer. Tho use of the oscilloscope is again desirable 
for tho rapid location of tho fault. It should not be overlooked 
that quite high voltages can bo found throughout the feedback 
circuit, and small mica condensers will sometimes fail or develop 
an intermittent fault producing picture interference. 

Cathode-ray-tube Faults 

Tho modern cathode-ray tube is a precision instrument, and 
should last, in regular use for at least two years without serious 
deterioration. In the past the most common reason for tube re- 
placement was the presence of a relatively insensitive area of tuhe 
fluorescence due to heavy ion bombardment from tracos of gas in 
t he tube. In most modern tidies this defect is overcome by means 
of the " ion trap ", tho presence of which is usually recognisable 
by the deliberate off-centre alignmcntof the cathode-gun assembly. 
A small permanent magnet clamped externally near the tube base 
deflects tho lighter electron beam into the accelerating electrodes, 
leaving tho ions behind in the " trap ". It is important to ensure 
that the small correcting magnet is adjusted for maximum 
picture brightness before a set is sold or returned to the customer 
after servicing. Dull pictures and shortened tube life will result 
from incorrect adjustment of the ion -trap magnet. 

Probably the most common cause of tube failure is due to a 
breakdown in the heater-to-cathode insulation. This defect 
causes blurred definition and uncontrollable tube illumination 
with complete loss of picture modulation. Sometimes the tube 
will function normally after the set has been switched rapidly off 
and on, but the trouble returns more and more frequently. 

There aro temporary measures for this defect, such as r intr 

the tube heater from a floating winding on a separate heater 
transformer. Some improvement can usually be effected by this 
measure, but unless the transformer is a specially constructed 
component with a low inter-winding capacity, most of the video 
detail at high frequencies will be lost. Grid-to-cathodo shorts 
rarefy occur, and aro usually accompanied by a " click " from tho 
tube, the screen of which flares brightly as the bias disappears. 
Very occasionally a tube may show a faulty heater connection 
which may occur in the base connection. If this condition is 
suspected, the application of solder and flux may effect a cure. 
It occasionally happens that the tube E.H.T, connecting cap 
becomes disconnected and the wire broken off in the glass seal. 
A satisfactory contact may still be made by means of a quick- 



160 



TELEVISION ENGINEERS' POCKET BOOK 



drying, plastic metal compound available from shops dealing 
with model making. 

T. B. S. 

TIME- BASK KAULTS 

Time-base troubles account for a high proportion of the faults 
in which the resulting picture appears in u distorted or unsteady 
form, while faults in the line time-basc/E.H.T. circuits aro also 
a common cause of a complete absence of raster. Owing to tho 
divergences in the circuits, similar faults in different time-bases 
may produce very different symptoms, but (lie following notes 
are generally applicable. 

Line Time-base Faults 

If the line oscillator is not functioning no E.H.T. will be pro- 
duced, and thero will bo a complete ubsence of raster. If it is 
functioning, but at an incorrect speed, the picture will either not 
lock and remain a complete jumble (indicating an absence oi 
synchronising pulses) when the line hold control is varied or will 
lock with several side-by-side images repeated across tho screen, 
indicating that the speed is too fast. 

That (he oscillator is functioning may bo indicated by the 
presence of the 10-ke/s whistle, but, since this whistlo comes 
mainly from tho line output transformer, its absence is not- a Una) 
test of" non-oscillation. With a blocking oscillator e useful check 
is to measure the voltage with a high-resistance meter between 
the grid and chassis: oscillation is then indicated hy a negative 
voltage. 

Where the speed of a blocking oscillator is too fast, this may 
be duo to failing omission of tho valve: high-resistance windings 
OX leaky insulation in tho blocking transformer; or a faulty 
oonde&sex between tho M earthy " end of the grid winding and 
chassis. 

Where the speed of a blocking oscillator is too slow, the most 

likely cause is a resistor increasing in value, usually in the net- 
work which Iced- I hr positive bias voltage In the " earthy " side 
of the grid winding of the blocking transformer. 

With multi-vibrator circuits, too fast speed may be causod by 
low emission of the valves: low capacity or leakage in the grid 
condensers or change in the networks, if any, supplying the bias 
to the valve. Too slow a speed is often due to a resistor having 
gone "high"; suspects should include the anode and screen 
feed resistors and the grid resistor networks. 

Line Output Stage 

If the oscillator is functioning but there is a complete absence 
of raster the fault is almost certainly in the line output stage. 
First cheek the throe valves: the line output, the efficiency diode 
and the H.H.T. rectifier. Failure may also bo due to a short- 






FAULT FINDING 




i> 



162 



TELEVISION ENGINEERS* POCKET BOOK 



circuit, or " damping " across the output windings of the lino 
output transformer (e.g., shorted turns in the transformer or 
in the scan coils, or leakage between lino and frame scan coils). 
For some receivers a quick check for clamping across the secondary 
is to unplug the scan coils, but care must be taken to avoid the 
risk of burning tho screen. Also check any screened leads 
connecting the scanning coils for breakdown of insulation. 

Cramping 

Cramping on the left-hand side of tho picture, with a dark 
border showing along the mask, may be due to lack of emission 
in the efficiency diode, or to a high-resistance joint in the wiring 
to this valve. 

Cramping on the right-hand side of the picturo is most likelv 
due to failing emission in the line output valve, but mas r be 
caused by insufficient power being applied to the heater {for 
example, duo to wrong setting of the mains adjustment panel) or 
due to the screen feed or cathode bias resistor, if any, having 
increased in value. 

Cramping at the centre of the picture (Tost Card " C " showing 
an " egg-shaped " central circle) may be due to a fault in tho 
cathode circuit (e.g., faulty cathode decoupling condensers) pro- 
ducing negative feedback, or to an incorrect waveform being 
applied to the output valve, either due to a fault in the oscillator 
stage or in tho correction network in tho grid circuit of the output 
stage. 

Frame Time-bases 

Tho absence of frame scan output will result in a thin bright 
horizontal line across the screen, and when investigating such 
a fault take rare to keep the " brightness" control as low as 
possible in avoid burning the screen, 

A quick check to locate whether the fault is in the oscillator or 
output stage may be made by touching, as in sound receiver 
practice, the grid of first tho output and then the oscillator valve 
(tako care that the chassis is not at " live " potential). If the 
valve is working the thin line will open up a little due to hum 
pick-up. If there is no effect on tho thin lino it indicates that the 
valve is not working or that the grid circuit is short-circuited to 
chassis. Faults Ukely to produce incorrect speeds, etc., in the 
frame time-base follow roughly similar linos to thoso described 
for the line time-base circuits, "although the frequencies involved 
are much lower {50 frames per second). 

If the oscillator is running too fast the picture will appear to 
bo moving downwards; if too slow tho direction will appear to 
be upwards. 

Insufficient Height.- Check output and then oscillator valves 
for low emission, anodo feed resistor on the oscillator valve and 
grid resistor on output valve. 



FAULT FINDING 



163 



Cramping at Top.— Check the components in the negative 
iced back correction circuit, if any, between the anode and grid 
of the output valve. Check the grid coupling condensers for 
leakage. 

Cramping at Bottom. — This may bo due to faulty emission or 
the frame output valve or loss of capacity in the cathode by -pass 
condenser. Faults in the negative feedback correction compo- 
nents may also give rise to this effect. 

Synchronisation Faults 

Where the fault is due solely to poor or absent synchronisation 
pulses it should be possible to obtain a picture momentarily by 
manual adjustments of the hold controls. 

Where it is possible to lock the frame but not the line 
oscillator, the fault is most likely to bo in the differentiating 
circuit or in any fly-wheel synchronising circuits which may be 
lined. 

When the line but not the frame oscillator can be locked the 
fault may be in the integrating circuit or in the interlace filter 
which may he used to eliminate line pulses from the frame syn- 
chronising pulses. 

Poor hold on both oscillators may bo duo to the synchronising 
separator valve failing, incorrect screen voltage due to feed 
resistor increasing in value or leakage in tho by-pass condenser. 

If the line hold only is weak examine the line synchronising 
feed condenser. Where line tearing is pronounced, it may bo 
due to the coupling components in the grid circuit. 

LINK OUTPUT TRANSFORM ERH 
The lino output transformers in modern receivers arc subjected 
to severe voltage and current -stresses, and it is not surprising 
that these occasionally tail. However, it is sometimes too 
quickly- assume:! that any failure* in the line scan or K.H.T. 
circuits, if not caused by valve failure, must be due to the output 
transformer. Many ol the output transformers which are re- 
turned to manufacturers as " faulty " are subsequently found 
to bo in good order. Tho following notes, based on information 
prepared by Alfred Hose, M.I.R.E., of Direct TV Replacements, 
offer useful guidance on this subject. 

The following arc some of the faults which may induce symp 1 
tonas similar to those of a faulty line output transformer; 

(a) Deflector coils with shorting turns, open-circuit wind- 
ing or leakage between windings, or from winding to core. 

{!>) F.H.T. rectifier valve having gone " soft " or having 
an intereleetrode short-circuit. 

(r) Leakage due to incorrect routeing of wiring to the 
output transformer, 

(r/) Short-circuited line linearity trimmer (a fault very 
often overlooked) or a short -circuit in the associated com- 
ponents. 



164 TELEVISION ENGINEERS' POCKET BOOK 

(e) Corona occurring at. tho anode cap of t lie picture lube, 
or :ii I In- connecting wires lo the E.H.T. rectifier. 
(/) The picture tube taking excessive E.H.T. current. 
((/) Incorrect lino -sliced. 
(A) Faulty biasing on tho line output valve, 
(■/) Faulty width coils. 
(j) Faulty elTieiency ilioilo. 

Tho following are some suggestions for tests which can be 
earned out on suspected output (runsforniers, particularly where 
those are fairly new or recent ly rewound : 

(1) Make a careful visual examination. For example, when 
wiring a transformer into the set. tho heat of the soldering-iron 
may easily release fine wires corning from the windings. 

(a) Check the tappings carefully to ensures that both wires are 
connected to the tag. 

(.'J) Check that solder has not been dnippnil on to a winding 
and so causing short-circuited turns. 

(•*) Cheek that tho windings have not been knocked, or that 
the windings have not been damaged by a slipping screw-driver. 

(f>) Listen for the 10-kc/s whistle : if this is present but there 
is no E.H.T., suspect the heater circuit of the E.H.T. rectifier. 
A useful test, is to disconnect the rectifier heater winding and 
connect the E.H.T. rectifier to a well-insulated battery, Should 
E.H.T. then appear, cxamino the picture and watch the effect 
of connecting one side of the heater winding to the rectifier (note 
this will be at E.H.T.). If corona then appears, or tho picture 
lades away, the must Mkeh cause is poor heater- winding in- 
sulation. Should the picture not be affected by connecting the 
healer winding, the most probable fault is insufficient drive. 
Where heater insula! ion leakage has been confirmed, it is possible, 
in certain cases, for example, where a U2f> valve is concerned. 
to obtain a small heator-isolaled transformer; tins will avoid 
replacing the output transformer. Warning: Do not touch the 
batten when making the above test, as its ease will be at K.II.T. 

(6) Check the transformer under working conditions in a 
darkened room, as corona and arcing can be detected most easil] 
in this way. Corona is usually caused by sharp points on soldered 
joints or sharp wire ends. 

(7) Always check that the cure: i lypo of rectifier valve has 
been fitted. 

(8) Remember that the D.C. resistances listed in service in- 
formation are intended as a rough guide only. Actual values 
may differ appreciably on each batch of windings. Then, again, 
some manufacturers have substituted different gauge wire in 
replacement transformers, for example a heavier gauge wire w iili 
less D.C. resistance may be used to prevent overheating. It 
amy also be found that the resistance of the E.H.T. overwind 
is very much greater than that specified. This may be due to 
the use of resistance wire in order to overcome stria! ions (such 



FAULT FINDING 



165 



n- winding ma\ he about 4,000 ohms instead of the 2(1(1 ohms 
specified in the original data). 

(!)) Where the E.H.T. increases greatly when the anode cap is 
removed from the picture tube, suspect that either the tube is 
drawing excessive current or that the rectifier valve is faulty. 

(10) Many line output transformers are damaged by overload 
duo to tho lino drive control, if fitted, being wrongly adjusted, 
particularly after the replacement of a lino output valve. If a 
white vertical line appears at the left-hand side of the screen 
check that, tins control has been correctly set. Do not correct 
i he fault merely by altering the width control unless it has al- 
ivnil\ been confirmed thai tho circuit is working correctly. 



TURRET REPAIRS 

The ropair of faulty turret tuners often requires most delicate 
workmanship, and less skilled work is likely to impair rather than 
to improve results. It is for tins reason that many manufacturers 
recommend that turrets should always be returned to them for 
repair or adjustment. 

Kin- instance, the adjustment of the hand-pass I m nsfonuer 
coils between the H.F. amplifier and tho mixer is generally 
considered most inadvisable, as this opera! ion rcalh requires 
laboratory-type alignment equipment. Even tho adjustment of 
the oscillator and aerial coils should be tackled with care. 

The most frequent fault in turret tuners is oxidisation of the 
stud contacts, resulting in noisy or intermittent reception on one 
or more channels. The studs are readily accessible by removing 
the turret cover. Conventional switch-cleaning fluids, such as 
carbon tetrachloride, will remove the oxidisation but do not 
provide any |irolec(ion against the fault reoceurring and, unless 
used extremely sparingly and carefully, may attack the turret 
materials, A safer method of removing oxidisation is to polish 
tho studs with u dry cloth. Tho channel-selector mechanism 
on turrets should be kept lubricated, and after cleaning it is 
advisable to apph a smear of petroleum jelly to each si a tor 
spring contact. There are also available protective lubricants, 
such as " M.S. 4 " and ' l Electrolube ", containing water-repellent 
substances, and those provide useful protection against oxidisa- 
1 ion. 

Jt is important that no attempt bo made to increase contact 
pressure indiscriminately by adjustment of the spring contacts, 
although sometimes adjustment- to the switch-locating dovico 
will change tho point of contact slightly. The contact pressure 
should be adjusted only whero there is dearly a loose spring. 

A common cause of short-circuits is tho wearing off of tho 
insulating paint on the ends of tho small ceramic capacitors, 
leaving an exposed wire which may rub against another compo- 
nent. Faulty components may be tho result of overheating 
during soldering, either in manufacture or subsequently. 



166 



TELEVISION ENGINEERS' POCKET BOOK 



Where any tit tempt is mode to replueo a component, it is 

essential that the tuner should bo handled with great care, nnd 
that only an exact replacement, physically as well as electrically, 
should bo fitted in the precise position of the original component, 
with connecting wires oF the same length nnd path. 

Coils arc often adjusted by spreading their ends; great care 
should be taken not to disturb them accidentally. 

TROUBLE TRACING CHART 

Although the limitations of a simplified chart should be 
recognised, the following list of common symptoms and possible 
causes will provide useful guidance, particularly for the radio 
service engineer who has had relatively little practical experience 
of television work. 

Owing to divergences in circuit technique, symptoms of a 
particular fault may vary considerably, but the following sum- 
marised information is applicable to most modern receivers. 

MISCELLANEOUS PICTURE FAULTS 

While many picture faults provide by their symptoms an obvious 
clue as to the source of the trouble — linearity faults, such as 
cramping, insufficient height or width, for example, immediately 
suggest a time-base fault — there are a number of symptoms for 
which the location of tho trouble will prove puzzling to the new- 
comer to television servicing, but which, once recognised, provide 
no less valuable a clue as to the likely fault. 

" Ringing " 

This common picture fault, which takes the form of a black 
line immediately to the right of a white object, or a black line 
following a white object, is almost invariably caused by a dis- 
torted vision-response curve, providing excessive H.F. amplifica- 
tion. Response characteristics of this type tend to produce a 
series of damped oscillations in the tuned circuits, and these 
produce the effect already described. Where the fault is found 
when installing a new receiver, it often denotes mistuning of the 
local oscillator, while on older receivers it may either be due to 
local oscillator drift or to misalignment generally. However, 
where the fault develops suddenly and is accompanied by a marked 
reduction in the band-width of the receiver (as shown on Test Card 
C) and an increase in sensitivity, the damping resistors across I he 
tuned eiivniU should be checked. Faulty components iti the 
video compensating network of the video output stage, and i in- 
decoupling circuits, are other frequent causes of " ringing ", a 
useful pointer in this ease being that the receiver sensitivity 
may not be unduly affected. It should be noted that in some 
receivers, particularly those intended for " fringe " reception, a 
certain degree of " ringing " may be introduced intentionally to 
sharpen tho images; but since it is difficult to prevent such 









FAULT FINDING 



167 




168 



TELEVISION ENGINEERS' POCKET BOOK 



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172 



TELEVISION ENGINEERS' POCKET BOOK 



Instability from later becoming more pronounced, designers 
must bo wary of carrying this process too far. An effect somewhat 
akin to " ringing M may also be caused by "ghost" images 
(see pugo 142) produced by the arrival of signals at the receiver 
along multiple pot lis. 

"Line Ringing " 

Vertical bars on the left-hand side of the picture may be caused 
by " ringing ", i.e., damped oscillation, or the scanning coils or 
line-output transformer. With improvements in tho efficiency 
<if these components and the use of ellieiene\ and boost diodes, 
this fault has become less frequent; but in older models it is not 
uncommon for the high-wattage damping resistor {which is re- 
quired to dissipate considerable energy) connected across tho 
scanning coils to become open-circuited. On some modern 
receivers employing wide-angle tubes, a somewhat similar 
symptom may be caused by spurious signals from the lino- 
output valve beating with the local oscillator to produce an 
interfering signal ; the remedy is to provide a small high-voltage 
decoupling capacitance to the anode of the line-output valve. 

Sound-on-vision 

Alternate light and dark horizontal bars across the picture, 
occurring during the louder sound passages, and sometimes 
when severe destroying line hold, are the symptoms of this fault, 
Tho intermittent nature of the trouble will distinguish it from tin- 
effect of hum in the receiver. The fault may bo due to misalign- 
ment, general inefficiency of the sound-rejector circuits, or simply 
to slight oscillator drift which may be insufficient to produce 
other harmful effects. Another common cause — though ono 
that is not likely to arise after tho receiver has been working 
successfully is overloading of the frequency changer valve, ami 
this may bo cured by fitting an attenuator pad in tho aerial 
feeder. Other possible causes arc valve mierophony and feed- 
back in the H.T. circuits. 

" Pulling " 

" Pulling on Whites " is tho name given to a fault in which 
the picture is momentarily displaced horizontally whenever u- 
white image moves aeross the right-hand side of tho picture : 
it can most clearly be ol»-er\ <■,{ on Test Card C, when a castellated 
effect on vertical lines will be found to coincide with the changes 
from black to white in the right-hand border. It is caused by 
later triggering of the line-scan oscillator following a lino ending 
in white light, due to the receiver not responding to the ' front 
porch " preceding the line pulse. This may be due to poor high- 
frequency response of the vision receiver, and in this case will be 
accompanied by loss of the high definition patterns, or, where the 
patterns are unaffected, by loss of high frequencies in the circuits 
immediately preceding the synchronising separator; a likely 






FAULT FINDING 



173 









cause being high stray capacitance in the coupling between tho 
video amplifier and the grid of the synchronising separator, 

" Pulling on Blacks ", or as it is sometimes called " triggering 
on picture ", is a somewhat similar condition, but with the 
picture displaced in the opposite direction. The cause is almost 
invariably incorrect clipping in the synchronising separator; 
the clipping being above the 30 per cent black level, and thus 
allowing picture content to triggor off tho time-bases. A faulty 
component in the synchronising separator stage, such as an 
increase in value of the screen-feed resistor, is usually the reason 
for this condition. 

"Plastic " Picture 

Where the outlines of objects are clear but the picture has an 
overall grey appearance, the usual causo is poor L.F. response in 
the vision receiver or video amplifier, and any of the components 
or adjustments affecting overall response maybe at fault ; these 
include misalignment or incorrect local oscillator setting; a 
decrease in value of a coupling or by-pass condenser in the video 
amplifier. 

" Flare " or "Streaking " 

These terms are used to describe the condition when streaks 
or smudges appear to follow black-and-white images horizontally 
across the screen : the black horizontal bar at the top of Test Card 
C provides a most useful check. Tho cause is excessive L.F, 
response, which here again may bo caused by misalignment or 
defective compensation in the video -amplifier stage. A gradual 
increase in flaiiiiLT usually suggests misalignment or oscillator 
drift, whereas any sudden increase points to a faulty component, 
such as a decoupling condenser, or an increase in value of the 
anodo-load resistor in the video amplifier. 

Loss of Highlights 

A condition may sometimes be encountered where the darker 
shades of the picture are reproduced normally, but the lighter 
tones tend to flatten out and become almost indistinguishable 
from one another. This is caused by the peak amplitudes of the 
vision signals being lost by clipping, and is commonly caused by 
over-advanco of the vision-interference liniilcr, but may also be 
due to overdriving the cathode-ray tube or incorrect bias in the 
video-amplifier stage. 



[SECTION 13] 

ALIGNMENT 

by D. H. Fisher, A.M.I.E.E. 

Television demands the transmission of information covering a 
wide band of frequencies if the picture is to be accurately re- 
produced. In the easo of the British 405-line system the highest 
signal frequencies are approximately 3 Me/s, and if the transmitter 
is modulated in the normal maimer sidebands will extend to 



SOUND CARRIER 



VISION CARRIER 










J-'IC. 1.— T>OL'RT.E-SinF.BAXI> TRANSMISSION: 
(n) TRANSMISSION O'KVK; C'l liKl'KI VKU 
ELR3POW9B OOBVE. 



174 



(A) 



(B) 



ALIGNMENT 
SOUND CARRIER 



175 



VISION CARRIER 







Fin. 2.— ■ vestigial SHdsbahd Transmission: <a) Transmission Curte; {5} 

RaSPOKSJJ OtXKVfl AT DETKCTOU; ((*) MoDIKIKIl RHSPONSK CUKTX AT DETECTOR. 

i-3 Mc/s about the carrier. The double-sideband transmission 
curve is shown in Fig. 1 {a). 

At the inception of the British television service the first 
station, Alexandra Palace, operated hi this way, but the require- 
ments of a national service including several transmitters made 
ii noeoKsiiry (.<> use the availublo frequency band more efficiently. 



176 



TELEVISION ENGINEERS' POCKET BOOK 






Accordingly, vestigial sideband transmission has been utilised 
for all other stations. 

It is by no means necessary to transmit both sidebands in both 
sound broadcasting and television, provided that proper pre- 
cautions are taken. In the former it would probably be very 
inconvenient to dopart from standard double-sideband practice, 
but in the latter the saving effected is very important. Rather 
severe difficulties would arise if one sideband were completely 
removed, particularly with a high -power transmitter, and as a 
result a " vestige " is allowed to remain. Fig. 2 (a) shows the 
transmission curve for this system. 

Receiver Response Curves 

The television receiver must, in the amplifier stages before and 
after the detector, produeo equal gain over as much of the 
frequency band as possible. The response curvo of a double- 
sideband receiver will, therefore, ho of the nature shown in Kg. 
1 (ft). Care is taken to keep a level response vvil liin the passband 
and to achieve the greatest possible attenuation at the sound 
carrier {sound rejection). This requirement conflicts with the 
need to reproduce the extreme lower sideband frequencies, and the 
response normally falls off between 2-0 and 2-75 Mc/s. A very 
sharp fall off at the edge of the passband should be avoided, or 
high-frequency distortions — " rings " — will occur. 

In vestigial sideband transmission some arrangement must bo 
made for the fact that both sidebands are present up to 0-75 
Mc/s. In other words, double the energy is present, and if re- 
ceived without modification tho rectified video information at 
the detector will appear as shown in Fig. 2 (ft). The output 
up to 0-75 Mc/s will be 6 db, or 2 to 1 higher than the H.F. 
components. This may be overcome by letting the response fall 
off at a a toady rate from 0-75 Mc/s below to 0-75 Mc/s above the 
vision carrier. The fall-off rate should bo 8 db/Mc/s, tho carrier, 
therefore, being 6 db down from the top of the response curve as in 
Fig. 2 (e). Alternatively, tho carrier is placed at, say, 2 db down, 
and the video amplifier rn.spon.se curve is raised by 4 db at 
frequencies above 0-75 Me/s. 

The sound-channel responses are also shown on the diagram. 
Bandwidths of ±0-5 Mc/s are quite common for television sound 
channels. In the first place this helps in the problem of oscillator 
drift in superheterodyne receivers and generally makes tho circuit 
non-critical. Second, impulsive interference is more easily 
dealt with when amplified by a wide-band channel producing 
sharp pulses of a less objectionable nature. The sound channel 
must be well down at the vision-carrier frequency, where L.F. 
vision components would produce heavy interference. 

Forming the Response Curve 

The fairly strict requirements of tho response curve can bo 
satisfied in several ways. T.li.F, receivers using several stages 



ALIGNMENT 



177 



were often designed on the staggered-tnning principle (super- 
heterodynes as well, although, having rather less stages in the 

I .F. amplifier, more complex 

circuits are sometimes 

needed). 

The staggered -tuning 

principle consists of having 

a single circuit between each 

valve and adjusting its Q 

and tuning point to form a 

suitable combination with 

all the others. Fig. 3 (a) 

shows a five-circuit arrange- 
ment called a quintuplet. 

Trap or " sucker circuits " 

have been added to achieve 

extra attenuation at tho 

sound frequency. Traps T 1 

and T3 couple with 1.2 and 

L4 respectively to form a 

combined response curve in 

each case. T2 is in the 

cathode circuit of V3, and 

serves to lower tho gain at 
(he trap frequency. 

The second part, of Fig. 3 
shows how LI, L4 and Lo 
combine to give an approxi- 
mate response curve, and 
L2 and L3 sharpen the 
edges. Sound is taken from 
the junction of Tl and L2. 
TI, however, is not exactly 
tuned to sound frequency 
due to its reaction with L2. 
and the sound is coupled 
very lightly into U> so that 
interaction shall not occur. 
Fig. 4 {«) shows a two- 
valve amplifier suitable for 
a superheterodyne. The 
coupling between the mixer 
and V2, and V2 and V3 is 
by means of two circuit 
filters or bandpass circuits. 
Tho first uses mutual in- 
ductance coupling with a 

trap and sound take-off similar to the previous circuit. The second 
uses top capacity coupling, and a trap lias been added. Looking 
at the lower part, of the diagram, it can he seen that the combina- 
tion of L3. 1j4 and L."> produces nearly the required curve, which 




178 TELEVISION ENGINEERS' POCKET BOOK 

L4 L I L S 










RKSPOHSH OOttVEB SKK Flfi. 3 (a). 



is sharpened at the edges by LI, L2 as we saw in the previous 
arrangement. 

Pre-mixer Circuits 

In a superheterodyne receiver the precise response curve re- 
quired is always obtained in the I.F. circuits. The purpose of 
the pre-mixer circuits is to preserve this responso and provide 
extra attenuation outside the passband so that I.F. break- 
through, second-channel {or " imago ") or adjacent-channel 
interference do not occur. The gain before tho mixer must bo 
sufficient to render tho large amount of noise generated by the 
mixer negligible compared to the signal at its grid when operating 
at full sensitivity. 



ALIGNMENT 



179 



r^ + 




SOUND CHANNEL 

(a) 




INDIVIDUAL 



(b) 
Fin. 4.— Circuit ami RSSPOBSS OtntfU, Two-valve I.F. amflifucji. 

BAND I/III RECEIVER CIRCUITS 

The I.F. Amplifier 

Fig. 5 (a) shows tho complete circuit of the R.F. and I.F. 
stages of a receiver including a turret tuner. Although it is 
an economic design, the responso curve is to a higher specifica- 
tion that the circuits previously described and one of the band- 
pass couplings is complex. 

The operation of the circuit is, briefly, as follows: IFT VS 
is an over-coupled transformer providing a simple double humped 
curve as shown in Fig. 5 (b). Almost the entire overall curve 
sluipe is determined by the network between V3 anode and V4 



180 



TELEVISION ENGINEERS' POCKET BOOK 







£ Sao. y-^ 
—VWW 1 j"" ° 



hH 



^•i&l 



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ALIGNMENT 

Viston response at 1FT. V3 

Input level 50 mV. 
Input to V4 pin 2 (grid) 



181 




34-65 36-15 3815 

35-15 3715 

l-'iu. S (H 

Vision response at 1FT VI . 1FT V2 fl. Sfrid. Rej. 
Input level 7m V, 



Input to V3 pin 2 (grid) 



Sound Response at 1 F.T, SI & S2 

Input levels 

WOB:- 10 mV. ■ ' 

S/S :- 1-5mV. 

Input to V3 pin 2 (grid) 20dBs. 







3715 



36 15 
l-'n;. ((/). 
Overall Vision IF Response 



39 15 




Input to 
Tuner Test 

point 



3315 35-15 37 15 

h'lii. (tfj. 



182 TELEVISION ENGINEERS' POCKET BOOK 

Overall Vision R f Response 



Input level Banc! j = 60/«v 
Band Hji 110>iv 



> 4Dd a 



Input to Aerial Socket 







S -2 -1 V Adj. 
MC/s Mc's S 

1-n.i. j CO. 



Overall Sound I (-. Response 
Input level:. 

WOB> ImV 
S/C ; - 130/i v 




2V(WOB) 
S0mW(S/G) 



Input to Tuner Test 



grid and consisting of IKT VI (LI I), L20 and IFT V2 (L12). 
Lll and LIS am a bandpass pair, l.ioltom coupled by L20, which 
is bridged by <'-t. I '--"> and R20. This is known as a " bridged 
T " coupling, where L2II, C24 and < '2f> arc resonated at the sound 
frequency to produce a high degree of rejection by reducing the 
coupling between LU and L12. I12U is a balancing resistor 
which is chosen during design for optimum rejection with the 
minimum effect upon the vision response curve. The overall 
curve from \".i grid is shown in Fig. ,1 (c) and the sharpness of 
rejection is apparent. It is also seen I hat the overall shape is 
rounded. This shape is now being used by designers in an 
attempt to overcome picture distortions such as rings and over- 
shoots which arise with Hat-topped curves. 

The connection between Lll and the " bridged T M filter passes 
through the primary of TFT SI. There is a considerable amount 
of sound -frequency energy available at the input of the filter, 
due to its resonance, and in this way it may be passed to the 
sound amplifier VII. The mil-put of VI 1 is coupled to the 
sound defector via IFT 82, and the overall sound curve from 
V3 grid is shown in Fig. 5 (d). 

Tho circuit coupling the mixer in the tuner is a broad one, 
since it has to transfer both vision und sound. Also, the fames 
being a separate unit, the circuits IFT SV1 (L7) and IFT SV2 



ALIGNMENT 



183 









Q 








^ 


I 


UJ 


ox 

UJ 


a. 

s 


s 


> 


7 




5 


5 


5 






184 



TELEVISION ENGINEERS' POCKET BOOK 



(LI it) are coupled via a cable link. Lit is a trap circuit, couplet! 
inductively to L10 to produce a rejection at the I.F. produced 
by sound frequency interference from the next channel. Tha 
type of responso given by this network is broad and flat except 
for the rejection due to L9. The overall response at the gi id 
of V2 (tuner test point) is given in Fig. 5 (e). 

The Turret Tuner 

In the tuner (see Fig. y («.)), L4, L5 form a bandpass at sip ml 
frequency between VIA anode and the mixer (V'^'B) grid. The 
response is again broad to transfer vision and sound without 
affecting the overall I.F. curve. 

L6 is the oscillator coil appropriate to each channel, the 
oscillator voltage being fed into L5 by mutual coupling between 
the coils. L6 has a screw core adjustment. 

LI, L2 is the aerial circuit, a coupled transformer, forming 
with the rcsponso of L4, L5 an overall flat curve for the tuner. 
The overall curvo for the set is shown in Fig. 5 (/). 

It is essenl ial for the aerial circuit to be tuned corroetly to tho 
centre of the band for maximum gain and lowest noise on the 
picture (especially where signals are weak). LI, LO are tho 
only adjustments normally available in a turret tuner. The 
coils are built on to removable plastic " biscuits ", and flic inner 
coils L4, L5 are set- up and sealed in manufacture. Fig. 6 shows 
the construction of a typical tunor, and " biscuit ". Tho hole 
through which LB may be tuned is clearly indicated: LI may 
bo reached through an identical hole at the rear. 

All other adjustments in the tuner aro for manufacturing set 
up only, and should not be used unless a complete alignment is 
being attempted. 

The Switch Tuner 

A switch-type tuner can equally well be used, and the circuit 
of ikk; is shown in Fig. 7. Here, instead of having the aerial Rod 
oscillator circuits of each channel to tune when set to a given 
channel, all the oscillator circuits are available through the 
front (see Fig. 8). 

The aerial, K.F. anode and mixer -grid circuits have screw 
adjustments only for Hand 1 II as a whole and Band I as a whole. 

Because all the circuits are in series, alignment of any circuit 
must be done by working down from Channel 13, one channel at 
ti time. If, however, only one channel is in use in each band, 
it is permissible to use the adjustments appropriate to tho whole 
bands only, i.e., 



Maud 


Atrial 


li.f". Anode 


Mixer Grid 


Oscillator 


Hand III . ,1 LU J.ll 
tiaaii I . .1 L7 LIB 


L27 

L22 


L37 

T.35 



ALIGNMENT 



185 




186 



TELEVISION ENGINEERS' POCKET BOOK 




Via. a.— IsetUvMisNTAij Switch Hand I/III Tcnkh. 
(Pge, Ltd.) 

Normally only the oscillator circuit should bo considered and tho 

adjustment I'or tho appropriate channel tried first. 

The aerial circuit can well he trimmed after valvo changing. 
The makers' instructions alone should be followed when attempt- 
ing complete realignment. 

Intermediate Frequencies 

The first superheterodyne receivers used intermediate fre- 
quencies near 10-5 Mc/s for vision and 1-4-0 Mr s for sound. 
Inferfereiien problems proved serious. ;nnl ;j inovenienl was made 
lo 16-0 Mc/s vision and 19-5 Mc/s for sound. Difficulties also 
arose with these frequencies for sots tuning to Band 111 in that, 
the 'imago" was too close for good rejection and oscillator 
radiation was often high. Finally, B.K.E.M.A. sot a standard 
of 3465 Mc/s for vision and 38-15 Mc/s for sound. 

It is essential that I.F. amplifiers are aligned accurately to 
tho frequencies specified, otherwise interference problems and 
difficulty in aligning the tuner may result. 

A.G.C. 

Automatic Gain Control circuits ore now used on sound and 
vision circuits. The sound A.G.C. is often simple and consists 
of a connection via a smoothing circuit between tho detector 
output and I.F. valve(s) grid returns. The vision A.G.C. may 



ALIGNMENT 



187 



he more complicated and the R.V. stage may ha\e the A.G.C, 
voltage delayed. Makers' instructions should always be followed 
when aligning sots with A.G.C. When in doubt, apply — 2V 
approximately to the vision A.G.C: short-circuit sound A.G.C. 
and B.F. stago A.G.C. only when delayod. 

ALIGNMENT PROCEDURES 
Signal-generator Alignment, Band I Models 

Test gear requirements are detailed in Table 13.1 : 

Table 13.1 



ft'Tfl 



Signal cenerator 



i)l put indicator 



dmuectors and damper 



firmfirk* 



Should be the most reliable instrument, that can ho 
afforded. Frequency rant."; H)--'1M .Mc/s, Uut- 
put-Ievel indicator and calibrated attenuator 
important. LeakngemusthencgliRible. 

Universal meter 20,000 ohms per volt {not less) 
satisfactory. Alternatively 100 ft A f.s.d. meU-r iti 
series with 01) kilolnns (reading 5 V full scale). 

rice Kifj. U. 



The individual steps to bo followed in the alignment of tho two 
circuit arrangements shown in Figs. 3 and 4 are set. down in 
Tables 13.2 and 13.3. The routi no followed in each case is tho same, 
although tuning the bandpass circuits is a little more difficult 
than a simple tuned circuit. Basically, the output indicator is 
attached to tho detector load, and each stage is aligned indivi- 
dually, working back from output to input. At each step it is 
necessary to reduce the signal-generator input to keep tho output 
level the same. Tho output level should be limited to, say, 2 
volts, although various manufacturers may suggest different 
levels, depending upon the design. They may direet tho output 
reading to be taken from the output of the video amplifier ; other- 
wise, especially in cases of doubt, the detector load should be used. 

Whcro instability is suspected it is a good plan to connect an 
oscilloscope across the meter. Tho noise level will seem to rise 
if instability commences, or, if the signal generator is modulated, 
distortion of the waveform may take place. 

In Table 13.2 it has been assumed that the set is a T.R.F. for 
tho London channel. Each tuned circuit is tuned to a certain 
frequency ; this information is normally given by the maker, and 
varies from model to model. The figures in tho table are more or 
less what might bo found in a set of this type, but are for the 
purposes of example only. It is very important in most cases to 
tune the trap circuits before the accompanying signal circuit. If 
this procedure is not followed, interaction will occur and the 
alignment will have to be repeated. 



188 



TELEVISION ENGINEERS' POCKET BOOK 





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ALIGNMENT 



189 




Fin. ft («).— TKIIMINATHIN 111 Vl( ]■:. 



Tlif rfi,'n;il-L'i-iHir:itnr lerminat.iori derioe slmwti nliovc is In- 
tended EOT use wil h :x sigmil generator bnrinf; nu output imped- 
ance "f i he onltr of 7.j ohme, and should bn coTirieetcd in circuit 
when injecting arignal dfaeetto to tbe grid* of the* v;dvcs: it 
will not normally be required whoii LineeLiug gjgnate bo the 
nerial-iopBt socket of the receiver. The device shown below is 
fur tiniiijiiiig ttie [iriuiary winding of intcrmediiitc-frequcticv 
i r.i i i-.fornierii whilst the secondary winding is lieing adjusted, and 
■. ;i v rena. li in important ih.u tbg oroeodile elipa ra i 
el ee tricn 1 conne<:tiou with t-he receiver circuitry. For OOD- 
venieoea, botti units should bo made up and kept*:>vailalile f<»r 
nao wlii-n reqnired. 



SSOn IOOOP SUE6VIN6 




pro. B fj&).— Dawiso dkvh:k. 



190 



TELEVISION ENGINEERS' POCKET BOOK 



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ALIGNMENT 



191 



In the case outlined in Table 13.3 the same remarks, concerning 
frequencies, apply, and it is generally very important to keep 
exactly to the manufacturers' chosen intermediate frequencies. 
Tho damping device used should not be too bulky, and should be 
efficiently earthed. 

Signal Generator Alignment 0! Band I III Receivers 

The following procedure relates to tho circuits shown in 

Fig. 5 (a). 

The following equipment is required: ■ 

(1) An accurately calibrated signal generator giving C.W, and 
modulated output with an output impedance of 75 ohms, and 
having a range of 30-40 Mc/s for I.F. alignment, 40-70 Mo/'a for 
Band I and 170-200 Mc/s for Band III R.F. alignment. The 
eo-axial output lead should be terminated with an 82-ohm resistor 
(for I. F. alignment only) and tho connection leads from the 
terminated co-axial lead must be kept as short as possible. 

(2) A vision output meter. This may bo a 20,000-ohms/volt 
meter switched to the 10 V D.C. range (meter resistance not less 
ili;m 50,000 ohms), e.g., an Avo Model 8 (not an Avo Model 7) 
in series with a 5* 6k resistor on the hot side. Connect across 
K;S0. AUemativi'ly, a I ,tui(). ohms/volt meter switched to tho 
I -1 11 A D.C. range (meter resistance not more than 500 ohms), 
e.g., Avo Model 7 (not Avo Model 8), may bo used. Connect 
one lead to chassis, and the other in series with the earthy end of 
R30, by-passing the leads with a 1,000-pF condenser. 

(3) For use as an I.F. transformer shunt, a |-watt, Ik resistor 
in series with a 1,000-pF miniature ceramic condenser, with 
short leads, are required. 

(4) A sound-output meter. This may be a 3-ohm sound - 
output meter or an A.C. meter switched to the I -volt or 50-volt 
A.C, range. A 3-ohm sound-output meter should be connected 
across the sound -output transformer secondary in place of tho 
loudspeaker. If an A.C. meter is used switched to tho 1-volt 
A.C. range, it should he connected across tho sound-output 
transformer secondary: if the A.C. meter is switched to the 
50-volt A.C. range, it should be connected across the sound- 
output transformer primary. In either case the loudspeaker 
should he left connected or a 3-ohm load connected in its place. 

Procedure for LP. Alignment 

It is recommended that, whenever alignment of any stage is 
required, the whole alignment should be carried out. 

The signal generator output should bo connected to the tuner 
h'si point lor all adjustments, and the tuner switched to a Band 
1 II channel for which coils are fitted (but not a channel which 
the sot receives). Turn tho contrast control to minimum and 
the volume control to maximum. 

During vision l.F. alignment, adjust the input level of tho 



192 



TELEVISION ENGINEERS' POCKET BOOK 






unmodulated I.F. input so as to maintain 2 volts D.O. across, 
or 400 fiA through, R30. 

For sound I.F. alignment, use a 30 per cent modulated signal, 
null adjust the input level to maintain an output of 50 mVV or 
Of! V r.m.s. aeross the sound output transformer secondary, or 
25 V r.ims. aeross the sound-output transformer primary. 

Carry out the adjustments in the order given in Table 13.4. 

The correct tuning position for all cores except those specified 
in the following paragraph is the poak nearest the adjustment. 
end. 

The correct tuning position for the cores of IFT SI (L22), 
TFT V2 (L12) and IFT VI (LI I) is the peak nearest the top 
{above chassis). 

Note that LfJ will not tune unless L10 has been correctly 
adjusted, and thnt tho first operation must always bo the BOttnd 
rejector (L20). 

The signal-generator frequency setting should not bo disturbed 
when carrying out stops 1, 2. 3 and 4 in Table 13.4, and tho shunt 
should always be connected between the nearest point on tho 
chassis and the point specified in Table 13.4, using the shortest 
possible leads. 

When the I.F. alignment procedure has been completed, the 
overall sound and vision response curves should bo chocked 
against those shown in Fig. 5 (e) and [g). 

The procedure for aligning the circuits shown in Fig. 5 (<y) 
with tho use of a sweep generator is given later in this section. 



Tahi.e 13.4.— I.F 


. Alignment of Baxd I/III 


Rkctuvtcr 


Step 


Inject, 




Shll III 


Adjust 


Response 


Remarks 


1 


:;s.|.- 


C.W. 


— 


L2Q 


Min. vis. SoiiihI Rejection 


-' 


:ss-15 


Hod. 


— 


1,24 ('fop) 


Mux, sound 


s 


:is-ir. 


M...I. 


— 


L23 (Hot.) 


Max, sound 


-1 


38-10 


Moil. 


— 


Las 


Max. sound i Top peak 


i 


t'i 


screw IJo corn iHi-ih with base of former. 


i\ 


fiot M run- .In 


wn ft in. from tup of former (thU is npprox, working 


7 


SB- 78 


C.W. 


V-t pin 7 
(Anode; 


IJI illol.) 


Mux. vision 


8 


'Ait-lit 


C.W, 


^ *i.\ pin 7 
(Anode) 

v"8 pni 7 


lu crop) 


Miix, vision 


!i 


S6-75 


C.W. 


L12 


Max vision 


Top pnjik 








(Anode) 








lu 


M-W 


C.W. 


VI pin 'J 
(Grid) 


Lll 


Max. vision 




11 




Kepuui operations No. 7, 8, 9, 10. 


12 


35 


aw. 


— 1 JJQ(Hot.) | Mas. vision 1 


13 


::ti-7,j 


o.w. 


V:i pin 2 L7 1 Max. vision Top of Timer 
CGrid) 


It 


sj-is 


O.W. 


LB (Top) Min. virion 












ALIGNMENT 



193 



Sweep Generator (Wobbulator) Alignment, Band I Models 

Additional test gear requirements to those in tho previous 
section are given in Tablo 13.5. 

Table 13.5 



Item 



Remarks 



Sweep generator 
Oscilloscope 

Connectors . 



Sweep width 10 Mc/s. Other points as for signal 
generator. 

Required if no display in sweep generator, Should 
have bright trace of good linearity. Time-base 
must be locked to or driven from generator. 
Amplifier with low hum level essential— giving at 
least 1 in. deflection for 1 V input. 

As for signal -generator procedure. 



Procedure 

Although tho procedure is essentially the samo as in the signal- 
generator case, the use of a sweep generator is very desirable in 
that the full effect of any adjustment is clearly discornible. 
Thoro are, of course, disadvantages, but tho clear view of the 
responso of a part or complete amplifier is a great timo saver and 
assists hi producing more accurate results. 

It is necessary to havo some source of frequency reference, and 
for this purpose the signal generator is lightly coupled to the 



SWEEP GENERATOR 



OSCILLOSCOPE 





M 

IOO< 
(OOOpFjU* 



OUTPUT o+ 



UNIT UNDER TEST j\_vWW-(^)- 



tOO^A 
F.S.D. 



SIGNAL GENERATOR 



Fit!. 10.— AUItAXOKMBNT OP TEST EQUIPMENT KOK SWEEP G ITERATOR 
AUCNMKN'l". 



TELEVISION ENGINEERS 




ALIGNMENT 



195 




Pig. 11.— Kkrpossk uukvks see tarlks U.ti axu 13.7. 
Oorva Co) and (J) are shown with tho lower frequencies on the left, higher on tha 

ii-)il, for corn p;iris,m with the T.lt.K. stiiLVer-timed cirwiils. When, however, 
viewed on an oscilloscope set, np in the normal fashion, they would ;ippe:ir reversal. 

sweep input as shown in Fig. 10 (unless the wobbulator contains 
its own markers). The presence of the carrier at a frequency 
witliin the passband causes a beat pattern to form at tho time 
when the sweep-generator output passes this point. The 
pattern appears on the trace as a small blip, and can be made 
clear by restricting tho oscilloscope band-width to the minimum 
required for proper reproduction of tho waveform. The resistor 
and condenser across the oscilloscope terminals in Fig. 10 are for 
this purpose. 

Note that tho sweep generator is not really suitable for the 
alignment of the trap circuits. In Tables 13.6 and 13.7 the traps 
are Aligned initially with the signal generator connected to the input 
of the amplifier in question. The visual representation of the 



196 



TELEVISION ENGINEERS' POCKET BOOK 



r 



response curve makes it possible to accomplish the alignment in 
rather fewer steps than previously and permits a " halfway 
check " to be made, whereupon it should be fairly obvious 
whether the adjustment of the remaining circuits will produce the 
required curve. 

The sweep-generator input level is an important consideration, 
and should not be increased to a point where overloading sets in 
(this may give curves with ideally flat tops). The gain of the 
oscilloscope amplifier should bo set so that a 2-V input is always 
used. Furthermore, the marker input should be as small as 
possible. 

Sweep Generator I,F. Alignment of Band I/m Receivers 

The following sweep -generator alignment procedure is for the 
circuits shown in Fig. 5 (a). The tuner should be switched to 
an unused Band III channel for which coils are fitted, and the 
contrast and volume controls turned to ininimum. Connect, a 
L-o-V bias battery {negative lead) to the A.G.C. line at C27. 
The co -axial output lead from the sweep generator should be 
terminated with an 82 -ohm resistor (for I.F. alignment only) 
and the connection leads from the terminated co-axial lead must 
be kept as short as possible. For vision alignment, connect the 
sweep generator " Y input" to the junction of L15/L16. For 
sound alignment, connect tho sweep generator " Y input " to 
the junction of R85, R83 and C70. No I.F. transformer shunts 
are used. 

Tin; stages should be aligned in the following order: IKT St 
and S2 (to response curve shown in Fig. 5 (</)); IFT V3 (to 
response curve shown in Fig. 5 (&)); IFT VI, V2 and sound 
rejector (to response curve shown in Fig. 5 (c)). Then check that 
the overall vision and sound I.F. response curves are as shown 
in Figs. 5 (c) and 5 (</) respectively. Connect the wobbulator 
as indicated in tho figures, adjusting its output to maintain the 
cathode-ray tube trace amplitude quoted on each curve. 

Alignment o£ Band I Receiver R.F. Circuits 

There is, perhaps, more deviation botween manufacturers in 
the question of the pre -mixer or R.F. circuits than there is in 
general I.F. amplifier technique. Nevertheless, there are one 
or two basic points which must be realised. The oscillator 
must be tuned to the right frequency, and the R.F. circuits must 
be aligned for maximum gain, having a band-width sufficient 
to cover both vision and sound channels without disturbing the 
I.F. response already obtained. 

The best way of adjusting the oscillator frequency is to set the 
signal generator to the desired sound -channel frequency, and, 
feeding the output into the aerial socket, to set tho oscillator 
trimmer for maximum sound output. Care should be taken to, 
use a small signal, or the sound A.G.C. circuits (if any) will make 
the adjustment flat. 



ALIGNMENT 



197 



With only a signal generator available the R.F. circuits can be 
aligned by connecting the generator to the aerial socket and the 
meter to tho vision detector as before. The aerial circuit will, 
in all probability, be tuned to tho centre of tho desired band, and 
can be trimmed for maximum output. If followed by a bandpass 
filter the damping clip used for I.F. alignment will serve again. 
The overall curve can then be inspected. Note that an oscillator 
frequency higher than the signal frequency reverses the relation- 
ship between vision and sound carriers in the I.F. channel. 

Should there be only two pre-mixer circuits, they will be 
staggered, and it is probable that the resonant frequency of one 
will be near to the vision carrier and the other to the sound carrier. 
The maker's instructions in this respect must be closely followed, 
or some deterioration in performance under weak signal con- 
ditions must bo expected. 

Using a sweep generator (once the oscillator has been trimmed), 
it is possible to form an immediate idea of tho effect of the R.F. 
circuits. Due to the fairly wide band-width of any pre-mixer 
bandpass circuit, it is as well to use the damping clip as with the 
signal-generator method. The marker can bo set at the mid- 
band frequency and each circuit adjusted for peak response. 
Tho input circuit may be off trimmed within reasonable limits 
to balance tho curve shape. 



ALIGNMENT OF TUNERS 
Turret Tuners 

As has been indicated, it. is possible to carry out a number of 
adjustments on tuners, and the equipment needed is as indicated 
in Table 13.5. 

Most tuners have a test point — shown at " T.P." in Fig. 6 (a). 
The tuner must be powered exactly as in the receiver and the 
oscilloscope connected to the test point with the Y gain set 
according to tho tuner manufacturer's instructions, otherwise 
for a sensitivity of about 1 V for full deflection. 

The operation best carried out first is to set up all the oscillator 
frequencies. To do this it is either necessary to use a highly 
accurate wavemeter or to feed the signal generator into the aerial 
terminal set near to the right frequency and search about for a 
beat pattern on the oscilloscope trace. When this is found, the 
signal-generator output should be reduced to the minimum level 
before final adjustments to avoid " pulling ". The oscillator 
frequencies for channels 1-13 for the standard I.F. (34-65 Mc/s) 
are given below. For other I.F.s add the vision -carrier frequency 
to tho vision I.F. 



VlianneLi 


1 


2 


3 4 


5 


D 7 




Frequency (J/f/*> . 79*65 


86-4 


yi-4 


Wi 


lol-l 


214-4 


21D-4 





198 



TELEVISION ENGINEERS' POCKET BOOK 



Channels 


8 


9 


10 


11 


12 


13 


Frequenru (J/e/s) . 


224-4 


229-4 


234-1 


239-4 


244-4 


249-4 



Commence with channel 13 and work down, making &ure that 
the fine tuning control is set at exactly half rotation. Do not 
adjust CIO (Fig. 5) unless one channel will not centre with the 
screw core in its oscillator coil. When CIO has been moved, all 
oscillator coils will have to bo readjusted. When the R.F. 
circuits are to bo adjusted, connect the oscilloscope to the test 
point as before and the wobbulator to the aerial socket. Make 
sure that tho wobbulator output exactly matches the tuner 
input. If in doubt lit a 6- or 12-db attenuator. 

The signal generator may be used as a marker as shown in 
Fig. 10, and in each case tune the generator to the frequency 
midway between vision and sound. Tho vision, sound and mid 
frequencies are given below: 



Channel, 


1 


2 


s 


4 


!> 


G 


7 




Vision freq. (Mcjs) . 


45 


51-75 


56-75 


61-75 


66-75 


179-75 


184-76 




Mid freq. {Mejs) . 


43-25 


96 


55 


60 


65 


178 


183 




Sound freq. (Mejs) , 


ii-:. 


H '_'.-. 


53-25 J 68-25 


63-25 


178-25 


181-28 





Cttannrt. 


8 


9 


10 


11 


12 


13 


i'hi'm fn-f. (Mr.'s.i. 


188.78 


1 114-73 


i yj •:;. 


201-75 


209-75 


211-75 


.1/ id freq, {Mejs) . 


188 


193 


198 


203 


208 


21 W 


Sound freq. ( Mc{a) . 


186-25 


19185 


196-25 


201-25 


20C-25 


211-25 



With a turret timer start at tho highest channel and work 
down. Net up the equipment to produce a curve and tune tho 
aerial coil to produce maximum curve height at the mid frequency. 
II. oiler .several eharmels have been sn adjusted, there is a. severe 
tilt, to the curve on all, C8 or Cll (Fig. 5) should be adjusted for 
a level curve. Then recheek all channels. If there is a trimmer 
condenser in tho aerial circuit, it should not be moved unless 
the aerial slugs cannot be moved to reach the desired tuning 
point. After such an adjustment, retuno each aerial coil. 
Tuner curves should fall within tho limits shown in Fig. i> (/). 
Do not try to reset the K.F. anode and mixer grid coils: it is 
best to obtain replacement biscuits. 

{Continued on page SIT) 






INTERMEDIATE FREQUENCIES 
Tabus 13.7. — Television Beceiver I.F.s 

Models marked • are aligned to upper sideband 



199 





Vision 


Sound 




Vision 


Sound 


Model 


/./■'. 


T.F. 


Model 


I.F. 


l.F. 




(Jfc/*) 


(Mcjt) 




(Mc/s) 


(Mejs) 


ACE 






ALBA (contd.) 






Astra 


13-3 


9*8 


T744KM 


34-5 


88-0 


Capelia 


13-3 


9-8 


TflOfl 


34-5 


38-0 


Jupiter 


13-3 


9-8 


TR09872 


16-0 


iy-5 


Orion 


13-3 


9-8 


T 119872/ B 


lii-n 


19-5 




13-3 


9-8 


TK9S74 


16-0 


19-3 


VTO4S 


13-3 


9-8 


T11U0971 


16-0 


19-5 


688 


13-S 


9-8 


TRO0971T1 


16-0 


19-5 








TB/30973 


16-0 


19-5 








TRG1974 


16-0 


l;.,'. 


ALBA 






AMBASSADOR 






MT841 


1 10 


10-5 


TVl 


15-75 


19-25 


ut;:i;2 


110 


10-5 


TV 2 


15-75 


19-25 


MT441 


14-U 


Jli-5 


TV4 


i .-.-::. 


19-25 


MT412 


11-0 


10-3 


TV5 


15-75 


19-25 


TS01 


16-tl 


lit- 5 


TV 7 


15-75 


19-25 


T301 


16-0 


19-5 


TV 7 It 


15-75 


111- 25 


T312 


16-0 


19-8 


T\ 1' 


15-75 


19-25 


T321 


3165 


38-15 


TV9F 


15-75 


19-25 


T324 


:;h;.- 


38-15 


TV lo 


15-75 


19-25 


T3S1 • 


T.K.P. 


T.R.F. 


TV10I! 


15-75 


19-25 


T33C 


31-5 


38-0 


TV10UC 


15-75 


19-25 


T336B 


34-5 


:ss-o 


TVloci; 


15-76 


19-28 


TXllil'M 


3-1-5 


88-0 


TV 11 


15-76 


19-25 


\".',r>'2 


ll-o 


10-5 


TV 1 ICC 


18-78 


19-88 


T372 


16-0 


19 -5 


'I'Vlin 


84-28 


37-73 


T372/B 


16-0 


19-5 


TVl-iTlI 


84-38 


37-75 


T392 


ItWl 


I'.i.'i 


i \ I rn : 


34-25 


37-75 


T391 


l.lii 


19-5 


T\ 15U 


31-25 


37-76 


'1411 


T.K.F. 


T.R.F. 


TVl&f'K 


:.i 25 


:!7-73 


T421 


T.ll.f. 


T.B.F. 


TV170 


84*28 


37-75 


T424 


31-65 


38-15 


TV1TCC 


34-25 


87-78 


T431 • 


T.K.F. 


T.R.F. 


TV17CI: 


31-25 


37-75 


T132 • 


T.K.F. 


T.R.F. 


TV171M 


31-25 


:i7-73 


T430 


84-68 


38-15 


TVl;n i 


::t-25 


37-75 


T472 


16-0 


19- 5 


T\ 19U> 


8446 


37-75 


T483 


16-0 


19-5 


TVllxT 


84*38 


37-76 


X48S/B 


16-0 


19-5 


TV111TM 


:,l ■•-■:. 


37-75 


T484 


16-0 


19-5 


TVMO0 


84-28 


37-75 


'l'-192 


1i;ii 


19-5 


TVSOOD 


31-25 


37-73 


T193 


l(i-0 


19-5 


TV2IX T 


84-28 


87*78 


T494 


16-0 


19-5 


TV2KJ 


31-25 


37-75 


TS04 


Hi-o 


19-5 


TV192T.M 


31-25 


87*78 


T524 


B4-C8 


■:.s-\;> 


2 1 < i ■ 


54-28 


37-75 


T524FM 


34-5 


38-0 








T53G 


34-05 


38-15 


ARGOSY 






T641 


31-5 


38-0 


• 04* 


14-0 


10-5 


TU44 


34-5 


38-0 


<rr\75 


14-0 


10-5 


T68B 


84*6 


B8-0 


i TV '51 7 


14-0 


10-5 


T8B8 


34-5 


:isii 


T2 


14-0 


10*8 


T71T 


34-5 


38-0 


T3 


14-0 


10-5 


'1721 


31-5 


38 o 


TT5/5 


14-0 


10-5 


T724FM 


34-5 


38-0 


TVI1I2I, 


ll-o 


10-5 


T741FM 


315 


38-0 


TV14I2B 


(4*0 


10-5 



38-8 Me/a sound and 37 Mi'/s vision in Hand 1/Ilt versions. 



200 



TELEVISION ENGINEERS' POCKET BOOK 





Vision 


Hound 




Vision 


Sound 


Model 


UP. 


r.F. 


Model 


/.F. 


I.F. 




l4/,'>) 


(Mcjs) 




I Mr, S} 


( Melt) 


ARGOSY (toturf.) 






BAIRD (cviihl.) 






14K41 


34-65 


5S-15 


T5614 


34-25 


37-75 


17U41 


:i4-K 


38-15 


TM17 


34-25 


37-76 


17F41 


:M-6f> 


38-15 


T5719 


34-26 


37-76 


17K40 


34-65 


88*16 


IG7S 


13-0 


9-5 


17K.41 


34-65 


38-15 


172S 


13-(i 


9-5 


17K43 


34-65 


US- 15 








21K40 


34-65 


; 38-15 


BANNER 






21L40 


31-65 


t 38-15 


B112 


16-0 


1 19-5 * 








ni ii 


34-5 


; 38-0 


BAIRD 






BU7 


34-5 


1 38-0 


Countryman * 


12-6 


9-1 


' B1170 


34-5 


B8-0 


l-.tiiMU-t .li.in 17 


no 


95 


B121 


16-0 


1U 5 


BTfirymso : "f sua 


T.U.F. 


T.U.F. 


j 11412 


W-0 


IS -5 


T29I" 


T.R.F. 


r.B.p. 


| lilll 


Ifi-u 


19-5 


Frotiislicr 1 1 


i::» 


9-5 


B416 


16-0 


1 9-6 


Shakespeare 1 7 


13-i» 


9-5 


. B136 


16-0 


19-5 


Townsman ° 


12-6 


9-1 


BT112 


lti-(i 


19*8 


11155 


T.U.F. 


T.U.F. 


BT1 14 


in-" 


19-5 


B175 


T.U.F. 


T.I1.F. 


IsTIK 


34-5 


38-0 


CI816 


13-il 


9-5 


BT1170 


34-5 


38-0 


0200: Ui. 1,2,4 


14-0 


10-5 








Ct». 3, 5 
08017 
C2117 


15-25 
13-U 


11-75 

9-5 

38-0 


BEAUMONT 

SI7/FM 


34-05 


3.vl5 


COG 14 


84*88 


37-75 


T 


34-6." 


88*18 


C6617 


31-25 


37-75 








rsti-ji 


34-25 


37-75 


BEETHOVEN 






08717 


34-25 


.17-75 


1177 


34-75 


38-25 


05720 


.14-25 


37-76 


B77C 


31-75 


38-25 


01)6617 


84-28 


37-75 


nao 


34-75 


88-88 


D2117 


34*8 


38-0 


R94 


34-75 


38-25 


pies* 


13 -r. 


9-1 


B94C 


34-75 


38-38 


F167 


18-0 


!i-5 


BOS 


84-78 


38-25 


1M712 


13(1 


9*8 


B98 


34-76 


38-25 


P1812 


13-0 


96 


1199 


.1-1-75 


38-38 


1T814 


i:sn 


9-5 


Bioe/i 


B4-78 


38- H5 


P1S45 


13-0 


9-5 


1 !•;<(:- 


31-75 


38-25 


PS014 


13-0 


9-5 


TV50 


T.R.F. 


T.U.F. 


P2017 


130 


9-5 


T\ 5i.UI 


'l'.lt.F. 


T.U.F. 


P21I4 


34-5 


38-0 








1'2117 


:: jr. 


38-0 


BOWJECTION 






T1 1 • 


T.U.F. 


T.U.F. 


Clubman 


16-0 


11-5 


T18 


T.U.F. 


T.Ji.F. 


11 k. 1 


16-0 


19-5 


ISO 


T.R.F. 


a-5 


Ilk. 2 


16-0 


19-5 


Til 


T.R.F. 


T.R.F. I 








T25 


T.U.F, 


T.R.F. " 


BUSH 






T26 


T.U.F. 


T.U.F. 


Mftn 


34-65 


38-15 


TM 


T.U.F. 


t.r.f. 


M69 


31-65 


38-15 


l'] IJ3 


[£•8 


9-1 


T.16t 


34-65 


38-15 


T164 « 


i-j-n 


81 


T97 


:ut;5 


38-18 


TIG5 » 


12-6 


91 


T67 


34 65 


:;.--i;. 


TI67 


13-11 


9-5 


1751 ' 


34-65 


38-15 


T172 


130 


9-5 


T780 


34 (15 


38-15 


T178S 


18-0 


9-5 


IN.M ' 


34 -115 


38-18 






• 130, 9-5 or 13-25, 9-75 (Binum-jIn-nO. 
f Earlier models have 34-6 Mc/s vision and S8-0 Me/a sound 



INTERMEDIATE FREQUENCIES 



201 





l 'ision 


."Sound 




Vision 


Sound 


Model 


t.F. 


/./'. , 


ihuht 


I,F. 


t.F. 




(.!/<■ a.I 


(Mr,:*) 




(Mcjs) 


(Mcts) 


BUSH (fiontd.) 






COLUMBIA (-..,'■/./.) 






T91 


T.R.F. 


0-725 ] 


060S 


13-0 


9-5 


T11U12A 


T.K.F. 


T.U.F. 


0808 


16-0 


19-5 


TRG12U 


T.U.F. 


I.U.F. 








TRG2I 


10-0 


19-5 \ 


COSSOR 






TUG 12 


T.i;.i-'. 


T.H.F. 


54 


6-0 


— 


TUG24 


10-0 


19-5 


66 


60 


— 


TUG26 


li;-o 


19-5 


137 


5-3 


— 


TUG 34 


16-0 


19-5 


237 


5-3 


— 


TUG 31 A 


li; ii 


19-5 


437 


5-3 


— 


Tuasa 


16-0 


19-5 


900 • 


8-0 


4GS ke/s 


TUG 360 * 


84-68 


88-18 


0016 


T.U.F. 


2-2 


TUG58 


3-1 -65 


38-15 


902* 


T.U.F. 


22 


TUG59 


34-G5 


:;- l:, 


912« 


T.U.F. 


2-2 


TUG68 


31 G5 


38-16 


914* 


T.U.F. 


2.2 


TUG K9 


34-65 


38-15 


Bi6 : 


130 


9-5 


TV I 


T.U.F. 


0-788 


917: 


130 


9-8 


TV2 


T.R.F. 


0-725 


918 


13-d 


9-5 


T\ II 


T.U.F. 


'l'.lt.F. 


919 


160 


19-6 


TV 12 


T.R.F. 


T.U.F. 


920 


160 


19-5 


TV82 


16-0 


19-5 


921 


16-0 


19-6 


TV24 


lC-0 


19-6 


923 


Ki-U 


9-5 


TV24C • 


34-65 


38-15 


924 


16-U 


19-6 


TV32 


16-0 


m-r. 


926 


lfi-0 


19-8 


TV 33 • 


84-66 


38-15 


y-iu 


16-0 


19-5 


TVSli 


16-0 


19-5 


927 


13-6 


10-1 


TV360 tt 


:il -68 


38-15 


928 


hi- ii 


19-5 


TV 43 • 


34 06 


38-15 


H2M- 


13-11 


IH-I 


TV53 


34-65 


38-15 


929 


130 


101 


TV58 


34-65 


38-15 


929 F 


13-6 


101 


tv<;-.' 


3-1-65 


38-15 


I 930 


15-H 


101 


TVC3 


84-68 


38-16 


B80P 


13-G 


1(1-1 


TVfili 


31-65 


38-15 


930N 


13-8 


10-1 


IV 75 


34-65 


3S 15 


1 930T 


13-C 


10-1 


TV 7(1 


34-65 


38-15 


1 930TF 


13-U 


10-1 


TV77 


84.66 


38-16 1 


980TN 


13-0 


10-1 


TV 79 


34-115 


55-15 


931 


13-6 


10-1 


TVW 


3165 


88-16 


931 V 


13-G 


101 


TY88 


84*68 


38-15 


932 


13-6 


10*1 


TV84 


84*68 


88-16 


933 


13-G 


10-1 


r\ 85 


84*68 


38- 1 6 


8831 


13-G 


114-1 


TV88C 


3I-U5 


38-15 


933N 


13-6 


10-1 


4-vst; 


34-05 


38-15 


934 


13-6 


10-1 


TV8GC 


84-66 


38-15 


034F 


13-0 


101 


TV9-1, 5, 6, 9 


34 05 


58-15 


934.V 


13-6 


10-1 


T\ jin G3 Rwuiver 


34-65 


38-15 


935 


34-6 


88-0 








937 


34-5 


88-0 








937 A 


34-65 


38-15 


CHAMPION 






938 


34-5 


38-0 


TV12T 


Itl-n 


19-5 


H38A 


34-65 


38-15 


TV17 


16-0 


J 9- 5 


9889 


34-5 


38-0 








;i3',i 


34-5 


38-0 


COLUMBIA 






939A 


34-5 


38-0 


i BUI 


14-0 


10-5 


939F 


34-5 


38-0 


oeoa 

- . 


14-0 


10-8 


968 


34-5 


38-0 



► Earlier models have 34-5 Mc/s vision and 38-0 Mc/s sound, 

+ Dual i-hmiiM"! l.F. Htrip. (10-7 Mc/s for radio,) 

; Some models, 19-8 Mc/a, 16 Mc/s. 






202 



TELEVISION ENGINEERS' POCKET BOOK 





Vision 


Smtnd 




Vision 


Sound 


Model 


l.F. 


r.F. 


Model 


l.F. 


l.F. 




(Mcft) 


(Mcft) 




(.Vc/*) 


(Mcls) 


COSSOR (contd.) 






DECCA (contd.) 






848 


3-1-85 


38-15 


131: Ch. 1 


13-0 


0-5 


11 u 


8448 


38-15 


Ch. 4 


14-0 


10-5 


U15 


3448 


38-10 


111: Cttlss, 5 


13-5 


10-0 


HI 5 A 


3-1 -65 


88-18 


Ch. Ids 


13-U 


9-5 


848B 


34-05 


88- 1 ;. 


Ch. 2 


184 


11-5 


948 K 


34-85 


3.-4-15 


Cli. 3, 4 


14-11 


100 


948 


34-66 


38-15 


222 


14-0 


10-5 


5117 


3448 


38-15 


300 


14-0 


10-5 


847A 


54-66 


88-18 


333 


14-0 


10-6 


MTV 


3448 


3X-15 


444 


34 05 


38-10 


948 


84-66 


68-16 


1000: Cli. Iss, 3, 4, 5 


14 


10-D 


!I48H 


64-69 


68-16 


Ch.-lds 


13-0 


9-5 


949 


54-65 


38-15 


Ch. 2 


15-0 


11-5 


1210 


64 


160 kc/3 


DEFIANT 






DECCA 






1*00 


8448 


38-15 


Beaudecca: Ch. 1 


IS-.i 


94 


Til! 


34-65 


38-15 


Uecola: Ch. 1 


i;;-<i 


34 


T17I 


:il-(i5 


38-15 


Ch. 4 


14 <J 


ln-O 


T172 


::h;5 


8-10 


Dual Unit; 






T170 


3-1-05 


38-15 


Oh. Iss, 3, 1, 5 


140 


10-5 


T141II 


8448 


38-15 


Ch. Ills 


184 


9-5 


T1710 


:;i-i;,j 


38-15 


Oh. B 


16-0 


Ll-6 


T172U 


34-05 


38-15 


Krn\-lUsl>rUlt»e: 






T17C0 


34-05 


3S-1,-, 


On. l 


13-11 


8-6 


T.V.H 


34-05 


38-15 


at. -i 


14-0 


1O-0 


TR9470 


13-11 


311-5 


Dl-l 


14-0 


10-5 


TR917CM 


14-0 


I '1-5 


1117 


14-0 


10-5 


5B847! 


13-0 


11-5 


1>I70 


14-0 


104 


TR947TM 


144 


10-5 


DMI 


34-66 


88-18 


TBI 247 


13-0 


y-o 


DM3/C 


84-66 


38-15 


TR1S47M 


144 


10-0 


D1C8 


54-66 


38-15 


TIU 24811 


13-0 


84 


DM3 C 


34-05 


88-16 


TU12S0Or, 


14-0 


III-,-, 


MM I 


34-60 


38-15 


TR125mM 


14-0 


10-5 


DMI c 


3 1 ■ 66 


3s- 15 


TKI25I1TL 


14-0 


10-5 


DM4/LBC 


54-69 


88-16 


TR1250TM 


14-0 


10-5 


DUS 


34-60 


38-15 


TR1252C 


14-0 


10-8 


DM l I 


34-05 


as -15 


T1U252T 


14-0 


104 


DM17 


31-60 


:>■];. 


TB1498T 


1 in 


10-5 1 


DM017 


34 -CO 


:w-l5 


TR1454/CB3 


34 


37-0 


mil 'in 7 


64-68 


38-15 


TRMoi/tk:; 


644 


37-5 


DMO/DI8 


84-66 


38-15 


TR1455/B3 


844 


:;:■;. 


DHO/D91 


8449 


38-10 


TR1I500 


340 


37-5 


I1M21/0 


84-66 


38-15 


TK1.i;,i;;i t 


34-0 


37-5 


DKSS 


84-66 


88-19 


TR1456T 


34-0 


37-5 


DM48 


84-66 


:>■];, 


TR1450TL 


S4-0 


37-5 


101 Mk. 1: Oh. 1 


13-5 


10-0 


TR1703C 


14-0 


10-5 


Ch. 4 


144 


llJ-5 


TR1753T 


140 


10-5 


1D1 Mk. 2: Ch. 1,4 


Mil 


10-5 


TR1754/CB3 


34 


37-5 


111: Oh. 1,4,5 


14-0 


10-5 


TR1754/TB3 


844 


37-5 


Ch. 2, 3 


15-0 


11-5 


TR1755/R3 


34-0 


37-5 


121: Ch. las, 5 


13-5 


10-0 


TR 17660 


31-0 


37-5 


Ch. Ids 


13-0 


9-5 


TR1756T 


34-0 


37-5 


Ch. 2 


15-0 


114 


TR175CTD 


34-0 


37-5 


Oh. 3, 4 


11 -it 


10-5 


41 


34-65 


38-10 



* Diml channel l.F. atrip. (111-7 M/os for.rndio.) 
t 15 Mc/s vision and 11-5 Mc/s sound for North and Scottish seta. 



INTERMEDIATE FREQUENCIES 



203 





1 ixiiiu 


Sound 




I'mon 


Svund 


afrdtt 


l.F. 


l.F. 


u„,i,r 


i.r. 


l.F. 




CJfe/*) | 


iitr M 




{Mela) 


(Mefa) 


DEFIANT (emit.) 






EKCO(f"«frf.') 






71 


34-65 


38-15 


T231F 


1G-0 


19-0 


72 


34-65 


38-15 


T283 


34-60 


38-15 


70 


34-65 


38-10 


T284 


34-60 


38-15 


410 


34-65 


38-15 | T293 


34-65 


::s- ] .". 


710 


31-60 


88-16 T3KJ 


34*65 


38-15 




8448 


381-5 ' T311 


34-68 


3815 


720 


34-65 


38-10 T312 


84-68 


88-18 


7i;o 


3405 


38-15 | T326 


34-00 


38-15 


14d3 


34-05 


88-18 


T327 


84-68 


88-18 


2109 


34-05 


38-15 


3380 


34-65 


88-16 


4109 


8448 


88-18 


T880P 


8448 


3S- 15 


7101 


84-66 


8* ■ I :. 


T331 


8448 


3S-15 


Tliiil 


84-66 


88*18 


3342 


:;4-i;r. 


38-16 


71n9FM 


84-68 


88-18 


3344 


3448 


58-18 


72i Ht 


8448 


38-15 


3348 


34-05 


38-1 5 1 


7009 


:u-i;;, 


38-15 


1386 


34-05 


58-16 1 


T0O9FM 


8449 


38-1 S 


T0138 


1G-2 


19-7 








TC140 


16-2 


19-7 


DYNATRON 






TG186 


16-2 


19-7 


B314/1 


20° 


23-5 o ; 


TCI 02 


16-2 


19-7 


£349 


20 * 


23-5 ° 


TC105 


16-2 


19-7 


paw a 


2" 


23-5 » 


TO160 


10-2 


19-7 


T\ 24 


2d ° 


23-5 * 


T0174 


1U-2 


19-7 


TV24A 


2ii° 


23-5 ° 


TC178 (early) 


16-2 


19-7 


TV2li 


194 


884 


TC17S (later) 


16-0 


19-5 


TT87 


19-5 


23-0 


'1VIS5 


16-2 


19-7 


TV27A, B, r 


19-5 


884 


TCI 90 (early) 


10-2 


19-7 


T\ - 2S 


350 




TCI 96 (later) 


16-0 


1U-5 


TVgfl 


34-5 


884 


TC20B (early) 


164 


19-7 


TV8SM 


844 


3S-1I 


T0200 (later) 


160 


19-5 


TV3U 


84-65 


58-18 


TC208 


lO-n 


lit-:. 


TV32 


84-8 


; - 


TCaoa 


16-0 


19-5 


tv;',:; 


$4-68 


MS- 15 


TC20SI/1 


8446 


38-15 


TY34 


34-68 


38-15 


TC220 


Kid 


19-5 


TV30 


34-85 


58-19 


It '22H/1 


3-1 -05 


38-15 


TV30F 


8448 


58-18 


T0348 


[64 


19-5 


TY37F 


34-05 


88-18 


T0S67 


164 


19-5 


TV88 


:; i ■(',:, 


58- 1 5 r 


TC207/1 


84-68 


38-15 


TV3SI/F 


34 -or. 


:is-i5 


Ti 21 W 


164 


39-5 


I'Vlil 


8448 


88-16 : 


T0268/1 


3446 


:;s-ir. 


ITiH 


;:i-ij;. 


38-10 


T0818 


34-68 


88-18 








TC313F 


34-60 


58-18 


EKCO 






n 846 


34-65 


88-19 t 


T141 


10-2 


19-7 


TGC310 


31-65 


38-15 


T161 


16-2 


19-7 


TO 13:; 7 


3446 


38-15 


T162 


10-3 


19-7 


TU 11272 


10-H 


1LI-5 


Tlii-t 


16-2 


iy-7 


TP808 


84-65 


88-18 


T165 


1C-2 


19-7 


Til 0124 


T.K.F. 


T.K.F. 


T205 (early) 


16-2 


19-7 


TR0139 


16-2 


19-7 


T205 (later) 


16-0 


19-5 


THCU24 


T.R.I''. 


T.K.F. 


T207 


10-0 


19-0 


TS46 


T.K.F. 


T.R.F. 


T2II1 


ic-ii 


. 19-5 


TS46/1 


T.R.F. 


T.R.F. 


T217 


16-0 


19-5 


TS88 


T.R.F. 


T.R.F. 


T221 


10-0 


1 19-0 


1 TS93 


T.R.F. 


T.R.F. 


T231 


16-0 


| 19-5 


TS100 


'i'.R.F. 


T.R.F. 


Lowlon hkmIi-Iv. 


Birmiiii.' 


mm li'ls are- 24-5 Mi-'s virion 


83 '•'■ ! -MHIid. 


f Dual channel f.F. strip. (10-7 Mc,s for radii 


-) 





204 



TELEVISION ENGINEERS* POCKET BOOK 








Vision 


found 




Vision 


Sound 


Mmlrl 


l.F. 


i.y. 


Model 


I.F. 


f.F. 




(J/r/a) 


{Mcjs) 




(J/e/s) 


{Mejs 


EKCO (sontd.) 






ENGLISH ELECTRIC (earud.y 




TBU4 


T.R.F. 


T.R.F 


urn IF 


:::>■:, 


39-0 


TS18S 


t.k.f. 


T.H.F. 


16T18 


35-5 


39-0 


TS193 


T.R.F. 


T.R.F. 


10T1SF 


35-5 


39-0 


TS1105 


T.R.F. 


T.R.F. 


1550: Oh. 1 


;.;.:, 


20-0 


T31114 


T.K.F. 


T.R.F. 


Ch. 2, 4 


18-0 


21-5 


TS030 


t.r.f. 


T.R.F. 


156011: Ch. 1 


16-5 


20-0 


28048 


T.R.F. 


T.H.F. 


Ch. 2, 4 


IS- II 


21-5 


TSC48/1 


T.H.F. 


T.R.F. 


1650: Ch. 1,4, 5 


23-5 


27-0 


TSC91 


t.r.f. 


T.K.F. 


Ch. 2, 3 


lin.il 


23-5 


i-soai/i 


T.H.F. 


T.H.F. 


1651: Oh. 1,4,5 


23-5 


27-0 


T3C93 


T.R.F. 


T.H.F. 


Oh. 2, 3 


20-0 


23-5 


TSU102 


T.R.F. 


T.R.F. 








TSCU'I 


i-.lr.i-. 


T.H.F. 


ETRONIC 






TSOl-18 


T.H.F. 


T.R..F. 


CV 105(1 1 


T.H.F. 


T.R.F. 


TSC193 


T.R.F. 


T.R.F. 


OV1250 f 


T.R.F. 


T.R.F. 


■l\-iOI102 


T.U.F. 


T.R.F, 


BOS3S31 


14-0 


II)-", 


TSC1113 


T.K.F. 


T.R.F. 


KS02231/1J 


14-0 


10-5 


Tsona-i 


T.R.I''. 


T.R.F. 


ECSS231/H/nM 


ltd 


10-5 


TU142 


1G-2 


1U-7 


l-:(.:»2231 HM 


1-1-0 


10-5 


TU1G9 


Hi- 2 


19-7 


EC VI 523 


14-0 


lO'B 


TU211 


1G-2 


19-7 


EOV1521 


11-0 


10-5 








EOF1527 


14 


10-5 


EMERSON 
B700 

E701 


34-75 
84-75 


3ft- 25 


ETV1627 
ETV1536 
KTYIG37 
HY203/A» 


14-0 
16-0 
16-0 

T.R.F. 


10-6 

19-5 

19-5 

T.R.F. 








HV203/B 


T.K.F. 


T. R.F. 


ENGLISH ELECTRIC 






HV204/A • 


T.R.F. 


T.R.F. 


C42* 


35-8 


39-0 


TTV2(Jl,l; 


T.R.F. 


T.R.F. 


i'12A 


34-65 


88*18 








(M2A.F.M. 


:;m;;. 


:;s-]r, 


FERGUSON 






042F.M. 


31-65 


38-15 


48 


34-65 


38-15 


CMS 


3405 


38-15 


103T 


16-0 


19-5 


C48A 


34-65 


38-15 


HtST 


10-0 


19-5 


C45A.F.M. 


34-65 


38-15 


UST 


16-0 


19-5 


045F.M. 


M-68 


38-15 


135T 


16-0 


19-8 


(J46 


34-65 


38-15 


143T 


16-0 


19-5 


C46A 


34-65 


38-15 


145T 


16-0 


19-5 


|'4(;a.F.M. 


3i-«r. 


38-15 


S03T 


34-65 


33-15 


(MSF.M. 


34-65 


:*■!.- 


204T 


34-65 


3B-15 


T40» 


35-5 


39-0 


205T 


34-65 


38-15 


T40A 


84*68 


38-15 


206T 


34-65 


38-15 


T4GA.F.M. 


84*68 


38-15 


21 ST 


34-65 


:;>-].-. 


'1 MCI P.M. 


31-05 


38-15 


81 4T 


34-65 


38-15 


T41 • 


35-5 


39-0 


21 7T 


31-65 


38-15 


I'M A 


34-nn 


38-15 


235T 


34-65 


::-i:, 


T-UA.FM. 


31-65 


:;-i.-> 


236T 


S4-65 


38-15 


T4IF.M. 


84*60 


:is-i;, 


S 1 IT 


31-65 


88*18 


16014: Oh. 1,4, 5 


23-5 


27-0 


245T 


34-65 


38-18 


Ch. 2, 3 


2U-0 


23-5 


2-IGT 


34-65 


38-15 


1G019 


350 


390 


24 7T 


84*88 


38-15 


16019D 


35-5 


39-0 


30BT 


34-05 


3815 


100198 


35-5 


as -ii 


•:,«v;y 


84-66 


38-15 


1GT11D 


35-5 


39-0 


807T 


34-05 


;;--\:> 



• 34-65 Mc/a vision and 38-15 Mc/9 sound on inter versions of these models (after 
Serial No. 15001). ' ' 

f London modela aligueti to upper sideband. 



INTERMEDIATE FREQUENCIES 



& »Jf. Utoit 10-7 Mc/B. 

t Diiui cliaiLiiel l.F. strip, (lU-7 AIl-,i- fur r-iiliu.) 



205 





Fwiwi 


Sound 




Vision 


Sound 


Model 


/./'. 


/./■'. 


Model 


l.F. 


l.F. 




(^/c/s.) 


(.1/c/j) 




(Mcjs) 


(Jf^#) 


FERGUSON (emitd.y 






FERRANTH '<■»" '<!.) 






308T 


::ior. 


38-15 


T136 


T.H.F. 


1010 


31 ST 


3-1-65 


38-15 


T1S8 


T.R.F 


T.H.F. 


am 


84-48 


38-15 


T138M 


T.R.F. 


T.K F. 


405T 


34-60 


88-U 


now 


34-65 


38-15 


U)GT 


:;i-o:> 


38-15 


jaoas 


34-65 


38-15 


4Q7T 


:;i-o:, 


S8-15 


T1002/I 


34-65 


38-16 


408T 


34-85 


38-15 


T1008 


34-65 


38-15 


1 1 61 


34-65 


88-18 • 


T1011 


84-65 


88*18 


f:ifiT 


:i|.i;:. 


88-18* 


TID2I 


34-65 


88*18 


188TC 


34*65 


38-15° 


T102:i 


:;t-r,r, 


88*16 


454T 


34-65 


::s-ir, 


T1023I-' 


34-65 


38-15 


.-.nfiT 


34-65 


:!s-ir. 


T1084 


■:.mr, 


:;■> i;,+ 


SOW 


31-65 


;w-i:. 


mas 


16-0 


19-5 


546T 


34-65 


88-18 


TU10 


T.H.F, 


io*o 


841T 


']'.R.F. 


T.R.F. 


Tianr, 


T.H.F. 


T.R.F. 


R41T/12 

812T 


T.R.F. 


T.R.F. 


TlSOSOf) 


T.R.F. 


'I'.R.F 


T.R.F. 


T.R.F. 


T12055 


||160 


19-5 


B48T 


T.R.F. 


T.R.F. 


T1215.| 


' 16-0 


19-5 


•MIT 


T.H.F. 


T.R.F. 


T1225 


fie-o 


19-6 


,'IIT.- 


T.H.F. 


T.K.F. 


T1246 1 


T.R.F. 


10-fi 


im:;t 


T.R.F. 


T.R.F. 


T1325P 


[<-.-< i 


in- E 


94STRG 


T.R.F. 


T.H.F. 


TMOftl' 


T.R.F. 


T.H.F. 


95 IT 


T.H.F. 


T.H.F. 


'I'MuutM) 


T.H.F. 


T.H.F. 


953T 


T.H.F. 


T.K.F. 


T1405S 


116-0 
116-0 


10-51 


WWTRQ 


T.H.F. 


T.H.F. 


T1415 


19-51 


957T 


T.R.F. 


T.H.F. 


*l t (25 


■ 16-0 


19-6 ' 


"iGM'l 


T.H.F. 


T.H.F. 


T 15115 


T.H.F. 


T.H.F. 


8681 - 


T.H.F. 


T.R.F. 


T 1505(11) 


T.R.F. 


T.H.F. 


878T 


T.H.F. 


T.H.F. 


T1808S 


10-01 


19-5 


B8OT 


16-0 


19-5 


T1805 


T.H.F. 


T.H.F. 


98 IT 


lfi-0 


111-5 


T10(l5M 


T.H.F. 


T.R.F. 


1IKST 


16-0 


19-5 


T1615 


16-0| 


19-51 


989T 


16-0 


l!»-5 


T1686 


16-0 


19-5 


9firtT 


18-0 


19-5 


T182.-. 


160 


111-5' 


990T(K) 


16-0 


19-r. 


TCI 004 


31-05 


38-15 


991T 


16-0 


19-5 


TC1005 


34-65 


88*18 


991T(X' 


16-0 


19-5 


TC1012 


34-65 


88*18 


HH2T 


Iti-.i 


1S!-S 


TOM1SB 


U-66 


S8-1S 


992T(N) 


16-0 


19-6 


TCliUS 


:-.i ■-;:, 


88*16 


!i;i:iT 


16-0 


19-5 


TOO1O10 


84-68 


88*18 


993T(K) 


10-U 


Hi-5 


'ITKiii'i 


8448 


88* 1 ■'> 


994T 


IG-0 


i'.i-r. 


14T2 


10.li 


19-5 


IWlT(X) 


10- II 


19-5 


14T3 


15-75 


19-25 


995T 


10-1) 


111- 5 


14T3D 


18*78 


111- 25 


995T(N) 


16-0 


I'.l .-> 


14T8E 


15-75 


19-88 


996T 


16-0 


19-5 


1 1T1 


i 16-75 


19-25 


996T<N) 


10-11 


19-5 


11T4F 


1 15,7D 


10-25 


997T 


16-0 


19-5 


14T5 


18*78 


19-25 


997T(K) 


160 


19-5 


14T8F 


15-75 


19-26 


998T 


ir.-<i 


111-5 


14TC 


15-75 


IK- 25 


998T(K) 


16-0 


lit-:. 


14TRF 


15-75 


19-25 








17K3 


15-75 


19*88 


FERRANTI 






17K3I) 


15-75 


lil-25 


T129 


T.R.F. 


'i'.i:.F. 


17K3F 


15-75 


19-25 


T129M 


T.H.F. 


T.R.F. 


17K1 


15-75 


10-25 



206 



TELEVISION ENGINEERS' POCKET BOOK 





Twi'wi 


S'iUIld 




i 'ishm 


.Sound 


Vote 


r.F. 


l.F. 


Model 


/./■: 


l.F. 




(J/c/*) 


i j/c;*) 




1.1/. -;.M 


(J/c/*) 


FERRANT1 (<•'■«'</.) 






G.E.C. (cokM.) 






17KIF 


15*75 


19*38 


1.T2! 17' 


T.H.F. 


T.H.F. 


I7K8 


15 75 


18-88 


818158 


84*68 


88*13 


17KSV 


i;. ■:;. 


18-25 


HT2253 


31-66 


38*16 


IT KB 


15-75 


Hi- 26 


BT8S64 


34*88 


38*18 


17KUF 


15-75 


1 '.1-2.1 


BT2148 


31-125 


87*628 


17SKI 


15-73 


19-25 


BT244U 


31-65 


38-15 


17SK4F 


15-75 


19-25 


RT8748 


34-125 


87*638 


17SK5 


15-70 


19-25 


BT27-15R 


31-65 


38-15 


17SK5F 


16-75 


19-25 


HT2747 


34-65 


38*16 


17SK6 


15-75 


19-25 


BT2743 


3166 


38-15 


17SK6F 


15-75 


19-26 


HT3251 


34-65 


38-15 


I7'J"3 


15-73 


10-25 


BT3252 


;: i •.;:. 


38-15 


irrsn 


15-75 


19-25 


BT8701 


3-D 


0-45 


17T8F 


15-75 


19-25 


BTSTOS 


3*0 


0-45 


17TI 


15-75 


19-26 


BT8747 


34*68 


38-15 


1 71 11- 


16*78 


19-26 


BT4641 


T.R.F. 


T.R.F. 


ins 


15-75 


L9-26 


BT4541U 


T.lt.F. 


T.H.F. 


1 71T.I.- 


IMC 


19-25 


BT-l.il 2 


T.H.F. 


T.H.F. 


im; 


15-75 


19-25 


HT4542U 


T.R.F. 


T.R.P, 


17T6* 


1 5-7.1 


19-25 


BTi 54 3 


84*138 


87*636 


2KTI 


15-75 


19-25 


BT4JH80 


31125 


37-625 


30T4D 


15-75 


111- 25 


BT4844 


311 88 


37*636 


2<>T5 


15-75 


1H-25 


BT4640 


13-3 


9-8 


S0T6 


].V7.-> 


l:>- 38 


BT46400 


11-3 


7-8 


21 K5 


15-75 


19-25 


BT4643 


34*186 


:.7-r,25 


3IK6 


15-75 


19*98 


I5TI7I3 


3 1 ■ 1 1.'". 


37-1525 


22 K 3 


15-75 


19-36 


HT5I44 


T.H.F. 


T.B.F. 


21KI 


15-75 


19-25 


BT51440 


T.U.F. 


T.R.F. 


24K4F 


16*78 


111- 25 


BTI148 


t.h.f. 


T.R.F. 


21K6 


15-75 


19-25 


BX5145U 


T.n.F. 


T.U.I'. 








BT8148 


31-125 


37*638 


G.E.C. 






ivi'r»n»;r 


84*138 


37*638 


BT012-1 


6-0 


2-5 


BT5147 


84*138 


37*625 


HT30S 


84*68 


88*16 


8170848 


34*136 


37-625 


BT808 


34*66 


SIM 5 


BT52-I8 


34-65 


38-15 


BTWM 


34 -(15 


88-16 


BTS3-I7 


34-65 


38*16 


IST306 


34-69 


88*18 


BT6548 


34*66 


88*16 


BTS06 


34-66 


8846 « 


BT5I4G 


34-65 


38-15 


BT308 


34*66 


88-18 1 


BX8648 


34-125 


37*62.1 


BT31H 


34-66 


88-18 


BT55 15 


34-65 


38-15 


HT811 


M-ea 


88*18 


BT664S 


84*138 


87*626 


RT812 


34*66 


88*16 


BT5643 


34-125 


37*636 


BT316 


84*68 


88*18 


BT6648B 


84*138 


37-625 


btiosia 


13-5 


10*0 


B3W148 


34-125 


87-688 


W30MB 


18-8 


9-8 


BT6145C 


:. 1 • 1 25 


37-625 


BT109K' 


11-3 


7-8 


BT65I1 


31-125 


37-1125 


BT109J 


13-3 


9-8 


BT654K. 


34-125 


37*636 


HTll.v. 


:-;.| •<;.'. 


38-15 


BT6.li 2 


34-125 


87*638 


BT1180 


34-65 


38*16 


HT(i641 


34-125 


87*638 


BTi 252 


::i- i-..-i 


38-15 


BT709S 


13-6 


10-0 


HT 13.14 


:vi-r,r, 


38-15 


BT7094 


13-5 


10-0 


BL'l 1 19 


31125 


37-625 


BT8090 


3d 


n-i; 


BT14SQ 


34-05 


88*18 


BT8121 


3-0 


0-15 


BT1M8 


84*128 


37-625 


BTSllii 


84*66 


38*16 


BTI 718 


34-66 


88*18 


BT8161 


30 


0*46 


BT2147 


T.ll.F. 


T.B.F. 


BTS215 


84*68 


:.-.-].-. 



I'.M. Unit 10*7 Mr a. 



INTERMEDIATE FREQUENCIES 



207 





Vision 


Smmd 




11 si "11 


Sound 


Moid 


i.F. 


l.F. 


Model 


/./'. 


l.F. 




(il/c/.-) 


(J/c/*) 




(Jfe/*) 


(J/f/j) 


G.E.C. (contd.) 






H.M.V. 1 <•<•»/(/.) 






BT8246 


34*68 


88*16 


1847 


31-65 


3S-15 


BT8348 


84*66 


88-16 


1843 


34-65 


38-15 


BT8448 


34*68 


38*18 


1850 


8-0 


4-5 


BT8646 


84*138 


87*628 


1K51 


T.H.K. 


T.ll.F. 


BT8749 


84418 


38-15 


1851 


34-fifi 


38-15 


BT9121 


6*0 


2-5 


1864 


34-65 


38-15 


BTB12S 


3-0 


ii- 1.". 


1 B68 


34-65 


88*18 


BX914-1 


12-8 


10*0 


1866 


84*66 


38-15 


Ml '.1343 


84*66 


38-15 


ISBT 


34*06 


38*15 








3868 


34*66 


3.8- 18 


H.M.V. 






L863 


84*68 


38*15 


9011 


I.B.F. 


■i if; 


187U 


34 .65 


38*18 


901 


■r.u.i'. 


1-5 


1S71 


84-08 


38*15 


91 12 


T.II.K 


46 


1878 


34.66 


88*16 • 


I" i*J. \ 


■r. in. 


ii- in 


!S7I 


34-65 


38*15 


903 


M-ll 


3-5 


1S76 


84*68 


38-15'- 


804 


8-0 


4-5 


1901 


8-0 


4-5 


306 


8-0 


4*6 


1902 


T.H.F. 


T.n.F 


80? 


8-0 


1-8 


1902 IS 


T.E.F. 


T.H.F 


I860 


8-0 


1-5 


2805 


34*0 


37*5 


1801 


S-ll 


1-5 


2806 


34*0 


37-5 


1802 


S-n 


4-8 


2807 


34*0 


37*5 


1808 


8-0 


6*8 


2803 


34*0 


37-5 


1801 


80 


4-5 


2811 


31*0 


37*5 


I8i>5 


'IM1.1'. 


T.B.F. 


2815 


34 


37-5 


1806 


T.B.F. 


T.B.F. 


2851 


340 


37*6 


]8n7 


'I'.ILl-'. 


'IMt.L-'. 


290 1 


31 11 


37*5 


1S.i7A 


'I'.U.K 


T.ll.F. 


2902 


31-11 


37-5 


ISHS 


T.R.P. 


T.H.I'. 


2902 H 


34-0 


37*5 


181 1 


r.ii.i-. 


T.lt.l'. 


3806 


84*0 


37-5 


1814 


31-0 


37-5 


3807 


340 


37-5 


isi.i 


T.n.r. 


'IMt.F. 


3811 


34-0 


37*5 


181 6 


34-0 


37-5 


3815 


31-0 


37*5 


1821) 


31-0 


37-5 


3801 


34-0 


37*5 


1821 


34-0 


37*5 


3902 


34-0 


37*5 


1823 


84*0 


37-5 


3902 B 


31-0 


37-5 


1821 


34 


37*5 


4806 


34-0 


37-5 


1821 A 


31-n 


37-5 


4851 


34-0 


37-5 


1825 


84*0 


37'5 


4902 


34*0 


37-5 


1S25A 


34*0 


37*6 


4902 B 


3|.(i 


37-5 


18241 


:;i-(i 


37-5 


5806 


34'0 


37-5 


L8964 


34-0 


37-5 


5651 


34-11 


37-5 


1827 


34-0 


37-5 


5902 


34-0 


37-5 


1827A. 


3-1*0 


37-5 


59(1211 


34-0 


37-5 


1828 


34-0 


37-6 








1829 


34-0 


37-5 


DWICTA 






1829A 


31-0 


37-5 


THil 


T.lt.l*'. 


T.ll.F. 


1830 


34-0 


37-5 


T102 


T.R.F. 


T.H.F. 


1831 


34-0 


37-8 


T103 


T.H.F. 


T.H.F. 


ISO' 


34-65 


38-15 


T104 


T.B.F. 


T.R.F. 


1841 


34-115 


38-15 


1T05 


T.K.F. 


T.H.F. 


1843 


:; i-i;5 


38-15 


T107 


T.B.F. 


T.H.F. 


1843 


34-G5 


38-15 


Tlos 


T.R.F. 


T.H.F. 


1844 


34-68 


38-15 


T110 


T.H.F. 


T.ll.F. 


1345 


:;i-f.;. 


38-15 


Till 


T.H.F. 


t.r.f. 


1846 


34-05 


38-15 


T112 


31*5 


38*0 



• f.m. 1 nit i» 7 He -. 



208 



TELEVISION ENGINEERS' POCKET BOOK 





Vision 


Sound 




Vision 


Sound 


Model 


I.F. 


l.F. 


Model 


I.F. 


I.F. 




(Mcfi) 


(Mcfx) 




(J/C/J) 


(.i/v,v) 


INVICTA (cunld.) 






KOLSTER-BRANDES (cmitd.) 




Tilt 


34-6 


38-0 


J1V40: Uh. 1,4 


16-6 


20-0 


tiis 


:sk. 


38-0 


Ch. 2, 3, 5 


13-9 


19-4 


T117 


34 -S 


38-0 


HV-IOF 


| 16-0 


19-5 


ins 


31-5 


38-0 


JF40: Uh. 1,4 


16-5 


20-0 


*1'U9 


34 -5 


38-0 


Ch. 2, 3, 5 


15-0 


111 1 


T120 


34-5 


38-0 


KF40 


16-0 


l'J-0 


118T 


34-5 


38-0 


KF50: Ch. 1,4 


16-5 


20-0 


HOT 


34-5! 


38-0 


Ch. 2, 3, 5 


15-9 


19-4 


120T 


34-5 1 


36-0 


KF60 


160 


19-5 


122 


:.H;r, 


38-15 


KV35 


16-0 


19-5 


123 


34-65 


;;*-i5 


KY50 


16-0 


19-5 


121 


31-65 


3S-I.1 


LFT50 


35-0 


38-5 


125 


34-65 


38-15 


LFTfiil 


35-0 


38-5 


126 


34-65 


38-15 


LFT100 


35-0 


38-5 


127 


34-65 


3815 


LVT30 


35-0 


38-5 


133 


34-65 


3915 


LVT50 


35-0 


38-5 


134 


34-65 


38-15 


MF50 


34 '65 


38-15 


130 


34-65 


38-15 


MV30 


34-65 


38-15 


137 


3465 


38-15 


MV50 


::!■<■,-( 


< 3S-I6 


138 


34-65 


38-15 


Mveo 


1 34-65 


38-15 


139 


34-65 


8-15 


MV100 


35-0 


38-0 


140 


34-63 


8*15 


MYJuo-l 


31-65 


38-15 


111 


34-65 


38-15 


NFBu 


34-65 


81-18 


149 


34-65 


88-15 


NF7D 


31-65 


38-16 


148 


84-66 


88-15 


NF70FM 


84-48 


88-18 


237 


34-65 


38-15 


NV40 


84-66 


3815 


337 


:;i-r,;, 


88-18 


OV30 


84-68 


88-18 


137 


34-60 


:;.-]:. 


UV3UFM 


84-68 


88-18 


587 


34-65 


88-15 


OV30/1 


34-85 


88-16 


889 


34-155 


88-18 


OK 100 


:uim 


38-15 


5870 


34-65 


38-15 


PV40 


34-65 


38-15 








FF70 


84-88 


38- 15 








l'V701-"M 


84-68 


88-16 


KOLSTER-BRANDES 






1'VllKl 


34-65 


:;*■!.-, 


CV40 • 


12-5 


9-0 


I'V 100/1 


:m-6;i 


88-18 


DV40» 


12-5 


9-0 


l'VF2u 


:;.l •(!:. 


88-16 


KQI00 


16-5 


20-0 


QV80 


34-65 


88-18 


KV3<) 


16-5 


20-0 


QVSO/1 


84-68 


88-16 


KV30T1 


16-5 


20-0 


(^v::<i 


14-68 


38-15 


KV30HM 


1..1I 


19-4 


QVSfl I 


34-65 


3S-I5 


KV30/L 


16-5 


20-0 


QVTO 


34-65 


88-18 


BV40 


165 


20-0 


McCarthy 






KV40B 


16-0 


21 Ml 


M0C1» 


T.U.F. 


T.IU\ 


EV40HM 


1 6-9 


in 1 


MCT1 • 


T.U.F. 


T.U.F. 


EV40/L 


165 


20-0 


TSUI 


6-0 


2-5 


HV50 • 


12-5 


'.)■» 


TSH3A 


(-..<■ 


2-5 


FT50 


16-5 


20-0 


TSH8B 


60 


2-5 


FV30 


16-5 


20-0 


TSH20 


60 


2-5 


FV40 


16-5 


20-0 


TSH212A 


6-0 


2-5 


HF40: Ch. 1, 4 


16-5 


20-0 


TSH212I1 


6-0 


2-5 


Ch. 2, 3, 5 i 


15-9 


19-4 


TSH2I2C 


6-0 


2-5 


HF60: Ch. 1, 4 


16-5 


20-0 


TSH3I2 


6-0 1 


2-5 


Ch. 2, 3, 5 ' 
1TT60: Ob. 1,1 


15-0 
16-5 


19-4 
20-0 


TSILtia/O 
TSH312/T 


6-0 | 
6-0 


2-5 

2-5 


Ch. 2, 3, 5 i 


15-9 


19-1 


T3U414/0 


13-0 


9-5 


HV20: Ch, 1,4 


16-5 


200 


T3H414/T 


13-0 


9-5 


Ch. 2, 3, 5 


15-9 


19-4 


TSH417 


13-0 


9<5 



INTERMEDIATE FREQUENCIES 



209 





FtttM 


Sotmd 




YUim 


Sun ml 


Mml.l 


I.F. 


/./'. 


MoM 


I.F. 


I.F. 




(Meft} 


(Jfe/») 




{Mc *) 


( J/c/*) 


MeMICHAEL 






MAKCONJPHOHE (.could.) 




De Luxe : Oh. 1 


13-0 


9-5 


VC61DA 


34-U 


37-5 


Ob. t 


23-5 


270 


TC6SDA 


34-0 


37-5 


C52 • 


84-a 


27-5 


V068DA1I 


34-0 


37-5 


U53 


34-5 


38-0 


VC69DA 


34 '0 


37-5 


C54 


34-5 


38-0 


VOJiiliAM 


34-0 , 


37-5 


0811 


34-6 


38-0 


VC73DA 


84-0 | 


37-5 


rii; 


31 -5 


38-0 


\ i -73 A 


14-0 


10-5 


C417F.M. 


:: t- ii.-» 


38-15 


VC76DA 


8441 


37-5 


('•1152 • 


24 


27-5 


VI S3 A 


14-0 


10-6 


01153 


34-5 


38-0 


H B6DA 


:,i -ii 


37-5 


UI154 

1 : 1! II J 


31-5 
34-5 
34-8 


38-0 
38-0 
38-0 


VC9SDA 

V0151 

V0168 


34-0 
34-0 
8441 


37-5 
37-5 
37-5 


M14T 


16 


19-5 


VHU52A 


l . i : - 1 


T-11.F 


MITT 


16-0 


19-5 


VR054DA 


T U.F. 


T.n.F. 


M17TLO 


16-0 


19-6 


VRC57DA 


T.lt.K. 


T.U.F 


M21T 


16-0 


10*8 


VU<:72A 


34-0 


37-5 


M2JTLO 


16-0 


19-5 


\ III 74KA 


3MI 


37-5 


M22T 


34-65 


3S-15 


\ i:c77i>\ 


8441 


37-5 


M 88 1 1 Vi 


:;i-ti3 


88-18 


VRC84DA 


34 


37-5 


M7IT 


:; l(;:, 


3S-15 


VUC87DA 


34 


37-5 


M73HFO 


34-65 


88-16 


VRC97DA 


B4-0 


37-5 


M 72T 


84-66 


38-15 


VTS'ia 


8-0 


4-5 


I474HFO 


84-68 


38-13 


VT53DA 


'[■.U.F. 


T.R.F 


M71T 


34-65 


38-16 


VT55A 


14 


10-5 


M274HFC 


84-68 


38-15 


V'1'561)A 


T.U.F. 


T.U.F. 


MI'll 


84-66 


88-18 


VTMDA 


8441 


37-5 


MI'HIll. 


:; i ■ 86 


88-16 


VT62HA 


31-0 


37-3 


Ml'17 


84-66 


3h-ir, 


VT63DA 


110 


10-5 


MP18 


:;i-6.-. 


88-16 


VT68DA/HM 


15-0 


11-5 


Ml' lit 


84-68 


83-18 


\ n;:;i)A/K»s 


15-0 


lt-8 


TM61 


84-0 


27-5 


\li;::i>A I. 


140 


10-5 


I'M 52 • 


i i -< i 


27-5 


VT631JA/M 


110 


10-5 


XM88 


84-8 


88-0 


VT63DA/X 


15-0 


11-0 


TM5IA 


34-5 


:;>-.i 


VT630A/S 


14-0 


10-5 


TM84B 


31-5 


8841 


VT68BA/W 


14-0 


U)-5 


TM317 


84-6 


38-0 


VT641JA 


844) 


37-5 


TM417 


34-3 


:;*n 


VT6&HA 


8441 


37-5 


129L 


2:;-;. 


2 7 -U, 2 ■" 


VT6RDA 


84-0 


37-5 


1 l".ISl ! 


23-5 


27-0/2-0 


VT68DAM 


r.i-n 


37-5 


512 


84-6 


27-5 


VT69DA 


31-0 


37-5 


5121EV 


24-0 


27-5 


VTfiUltAM 


■■'■" 


37-5 


909L 


23-5 


27-0/2-0 


VT73KA 


34-u 


37-5 


80880 


23-5 


27-0/2-ft 


VT75A 


14-0 


ln-3 


912L 


23-5 


97-6/9-Q 


VT76DA 


3-1 -d 


37-5 


;i t l>m 


98-8 


27-0/2-0 


VT83DA 


34-0 


37-5 


912 Special 


23-5 


27-0/2-0 


VT85A 


14-0 


10-5 


950L 


13 


9-5 


VT88DA 


34-0 


37-5 








VT160 


844) 


37-5 


MARCONIPHONE 






VT151 


:.i-" 


37-5 


VC52A 


T.U.F. 


T.H.F. 


VTI53 


:«-65 


.'•>- 1 -'- 


VC03DA 


' T.U.F. 


T.U.F. 


VT166 


84-68 


33-16 


VC55A 


14-0 


10-8 


VTir.i; 


84-66 


38-15 


V056DA 


T.R.F. 


, T.R.F 


\'l '167 


34-63 


88-16 


VU59DA 


34-0 


37-5 


VT158 


34-65 


38-15 


VC60UA 


31 ■'I 


;;:■:. 


VT13<.t 


3-1-65 


3816 



» 23-0 Mc/s vision and 26-6 Mc/s sound for channel 2 models. 



210 



TELEVISION ENGINEERS' POCKET BOOK 



iladtt 



Vision 

l.f. 

{Melt) 



MARCOHIPHONE (antd.) 



VTien 
VT161 
7nl 
702 

7i>;; 
704 
705 

706 
707 
709 
710 
711 
712 
713 

MASTERADIO 

I'TuO 
T409 

wis 

TS09 

T812L 

T6I2M 

T«12.\I 

T851 

T852 

T868 

188 I 

T855 

T917 

T1HN 

TD4T 

TWO 

T1>7T 

TH4C/3 

TB4T 

TE4T/3 

TK7C 

TE7C/3 

TK7T 

■r 1-7173 

TB21C 

TK1T 

TP7T 

TF21T 

TO4T 

TO70 

TO7T ■ 

TG810 
TG21T 
TTT4T 
f 1 3 7 1 
TH21T 
TJ7T 
T.T17 
TJ2I 
TRR52 



34-65 

34-65 
T.1U'\ 

T.K.K. 
T.lt.K. 

U-ll 

T.U.F. 

8-0 

e-o 

8-0 

«■(.( 
80 
8-0 

s-n 



15-75 
T.E.F. 

T.K.K. 

T.U.F. 

T.H.F. 

T.B.P. 

T.II.F, 

X.E.F, 
15-75 
16-78 
15-75 
18-78 
15-75 
in- 75 
18-78 
leu 
Ui-o 
16-0 
160 
16-0 
16-0 

ir. -ft 

I.M. 

Hi-" I 

te-o 

16-0 

la-o 

16-0 
16-0 
16-0 
160 
1G-0 
16-0 
16-0 
16-0 
16-0 
18-0 
16-U 
l«l-i) 
16-0 
10-75 



Sound 



:;s-i;, 
38-18 

ii- Hi 

1-5 

K- Hi 

5-5 

0*46 

-1-6 

4-5 

4-6 

4-5 

4-5 

4-5 

1-5 



19-25 
T.ll.K. 
T.H.I-'. 
T.B.F. 

T.H.F. 

r.Tt.v. 

T.H.F, 
T.lt.F. 
111-25 
19-25 
l;>-25 
l'J-25 
10-28 
23-25 
23-25 

tt-g 

IH-5 
19-5 
ly-5 

i n-5 

19-5 
19-5 
19-5 

lit-.-, 
19 -;» 
in;, 
19-5 
lil-5 
19-5 
19-5 
l;i.-, 
19-5 
19-5 
19-6 

i !-:, 

19-8 

Ill- 5 
]■.!-:> 
194 
09-5 
23-21 



AtlMtd 



MULLARD 
MTSS88 
KTS6Q1 
HTS881 

MTS68 1 



MURPHY 

\ 12V 
\W\ 
A 58 V 
VS6CA 
VIM 
VI 140 
\ ih; 
VU8C 
V]2u< 
\i::ic» 
V18SO* 
VI 5(1 
\ I7i;i 
VI7M- 
V181KJ 
V200 
V200A 
V202I : 
V302CA 

v><>\ 

V2H-H 

Villi 

V910C 

V2I4 

V2MA 
V216C 
V216UA 

V2:;n 

V2 (0 

V21HA 
73400 

V25II 

V2.H>A 

\ I'.-.i'Mi 

V250C 

VS600A 

V270 

V870A 

moo 

V2S0 
V880A 
V280AD 
V280O 

7281 II A 

vinoA 

V8000 

VUlO-sariea 

VSSO-eedm 

VMO-jseries 



Vision 


Sound 


/./■■. 


/,/•■. 


(Mejt) 


(Mcft) 


13-2 


9-7 


13-4 


9-9 


13-3 


9-8 


13-4 


9-9 


4-25 


0-75 


4-25 


0-75 


4-25 


0-75 


13-5 


10-0 


13-5 


10-0 


13-6 


10-0 


13-5 


10-0 


tS-8 


1<M) 


13-5 


10-0 


T.H.F. 


T.H.F. 


T.H.F. 


T.K.K. 


19-11 


1 5-5 


13-5 


Hi-n 


13-5 


Hin 


13-6 


KM) 


13-25 


9-75 


18-28 


9-75 


13-25 


9-75 


13-25 


9-75 


13-25 


:i-7.i 


13-25 


Ih?:. 


18-88 


il-75 


13-25 


!i-7.-i 


18-88 


9-78 


13-25 


9-75 


13-25 


9-76 


13-26 


9-75 


:.].,;:, 


38-1 r. 


3 Hi.", 


38-15 


34-65 


:is-ir. 


34-65 


38-15 


34-65 


38-15 


:;h;.i 


38-15 


84-66 


38-15 


34-65 


38-15 


34-65 


38-16 


31-65 


38-16 


:; 1 ■!;.-, 


38-15 


;:i (1,1 


38-15 


31-65 


38-15 


3-1-65 


38-15 


34-65 


38-15 


34-65 


38-15 


34-65 


38-15 


34-65 


3815 


84-08 


38-15 


34-65 


38-15 


:;i-H5 


38-15 


i-t-r.-l 


3-1.1 




6-31 



INTERMEDIATE FREQUENCIES 



211 



Xwtd 



['i.iinii 

I.F. 

(J/r/s) 



MURPHY icontd.) 
v i 10-eerlea 
7480-aertea 
V430-serics 

7440-sertaa 

VTT150 
VU200A 
VTF2KI 
VU210O 



PAGEANT 
F50 
P107 

I'Ki'.i 



PAM 
1908 
1909 
T968 

T954 
TM8 
BOO 
5000 

;.ni 

5(11 A 
.-,i 1 1 1-" 

517 

.117A 
M7i: 

.1171 A 

.1171' 

521 

.121 A 

5310 

5-21CA 

B81CF 

ii21F 



ML 
550FM 

.111 

.ill KM 
556 KM 

,Hii i F 
tiiinF 

tli.il> 

800V 

,.,..;- 

666 

G80P 

880S 

880 

7.KI 



84-68 

34-65 
94*60 

31-6.1 

19-0 

13-25 
13-25 
13-25 



34-65 
34-65 
:; i-r.ri 



16-0 

16-d 

31-5 

HI- 1 1 

31-5 

:;ir.-l 

84-68 

;;i-t;r> 

84-68 

34-155 

:;i-»;;, 

84-66 

:;i-t;i 
:!!-ti.1 
84-68 
84-68 
84-68 
::h;.i 
34-68 
34-65 
:u-«r, 
84-68 
84-66 
84-68 
:;!-(ii 
34-65 
31-65 

84-68 
84-68 

3-1 61 
34-85 
84-68 
84-68 
34-65 
31-65 
31-65 



Bemud 
l.f. 



:;s.|;, 

88-18 

88-18 

B-31 

88-18 

G-31 

15-5 

■.(■7.1 

9-75 

it- 7.1 



88-18 

38-15 
88-16 



in-:. 
m-r. 

38-0 
IW-1 

88-0 

88-18 

:;s-i:> 

88-18 

88-16 

88-16 

38-15 

38-15 

88-16 

38-15 

B8-18 

38-15 

38-15 

88-16 

88-16 

88-18 

88-16 

:;*■].-. 

88.15 

88*16 

38-15 

88-18 

3,s- 1 8 

38-16 

3S-15 

8806 
88-18 
88-18 
88-18 
88-18 
88-18 
38-15 



Mmkl 



PAM(c«H/d.) 
751 

752 UL 
753 
753(J 
754 
755 
7(11 
7650 
900 
901 
904 
008 
952 
953 
954 



PETO SCOTT 
TIM I 
Till 6/16 
TB18 
Till 7 
T\ 16/16 
T?W 
TV 88 
TV 12 I 
TV122 
TV 121 
TV 126 
TV 127 A 
TV 165 
TV188 
TV16U 
TVFJHi 
TV1411 
T\ I 1 1 21 
TV1414 
TV1415 
TV1416T 
■t'VI 418 
TV1419T 
TV1611 
TV1711 
TVI712i' ! 
TV1712T o 
T\I71I 
TV 171.1 
TV1716C 
TV1716T 
T717190 
TV17I9T 
TVI7L>n 
1 ISA 
17SA 
1422 

I 722 



I .-, J '»! 

I.F. 
{Mejt) 



31-65 

34-65 

34-65 

31-65 

34-65 

34-65 

34-65 

34-65 

35-0 

35-0 

34-5 

19-5 

3-1-5 

34-5 

16-0 



Xumid 

l.f. 

(Alc/st 



88*18 

38-15 

38-15 

38-16 

38-15 

38-15 

38-15 

38-15 

38-5 

38-6 

38-11 

16-0 

38-0 

38-0 

19-5 



12-8 


9-3 


34-65 


38-15 


84-66 


38-15 


12-8 


9-8 


:; i-iii 


38-15 


13-25 


[1-75 


13-25 


9-75 


13-25 


9-75 


13-25 


9-76 


13-4 


9-9 


13-1 


9-9 


13-4 


9-9 


13-4 


9-9 


13-1 


0-9 


13-4 


9-9 


13-1 


9-9 


13-4 


»•!) 


12-8 


9-3 


12-8 


9-3 


34-5 


38-0 


34-65 


38-15 


34-65 


38-15 


34-66 


3W-15 


13-1 


9-9 


13- 1 


9-9 


19-8 


9-3 


12-8 


9-3 


12-8 


'.1-3 


31-5 


38-0 


34-65 


38-15 


34-65 


38-15 


;.h;i 


38-16 


34-65 


38-15 


34-65 


38-15 


34 05 


38-15 


34-65 


3815 


34.-65 


31-15 


34-65 


38-15 



° Ocrtiiin models may be 13-4 Mc/a vision und 9-9 Mc/s sound. 



212 



TELEVISION ENGINEERS* POCKET BOOK 





Virion 


Sound 




Vision 


Sound 


Model 


i.r. 


I.F. 


Model 


I.F. 


I.F. 




(j/e/*) 


(J/c/*) 




(Mc/s) 


(Mc/s) 


PETO SCOTT (contd.) 






PHILCO (contd.) 






1723 


84-86 


38-15 


J 019 


34-65 


38-15 


1724 


84*88 


38-15 


1020 


34-66 


38-15 


1725 


84*88 


38-15 








1728 


34-65 


31-15 








1 72H 


.1465 


38-15 


PHILIPS 






1780 


31-65 


38-15 ° 


383A 


13-2 


9-7 


2128 


34-65 


38-15 <* 


385TT 


13-4 


9-9 








488A 


13-2 


9-7 








1S51: 


13-4 


9-9 


PHI1C0 






492U 


13-4 


9-9 


A 1457 


14-0 


10-5 


520A 


13-3 


9-8 


A11C7 


31-65 


38-15 


563A 


13-2 


9-7 


AM97 


34-65 


38-15 


600A 


13-4 


9-9 


AI497A 


34-65 


38-15 


663A 


13-2 


9-7 


A1557 


31-65 


38-15 


683U 


13-4 


9-9 


A.1707* 


T.R.F. 


T.R.F. 


701A 


13-1 


9-9 


A170R« 


T.R.F. 


T.n,F. 


79H.\ 


13-3 


9-8 


A1717 


14-0 


10-5 


1 10011 


12-0 


8-5 


A 1737 


14-0 


10-5 


1101U 


12-0 


8-5 


A 1 7 1 7 


14-0 


10-5 


llfilllK 


12-0 


8-5 


A1763C 


ll-ii 


10-5 


niiu 


12-0 


8-5 


A1753T 


ll-it 


10-5 


nin.iF 


12-0 


8-6 


A1767 


14-0 


10-6 


iimi:.\i 


12-0 


8-5 


A 1707 

A1777 


31-65 


38-15 


1 1 1 n r m f 


!2-0 


8-5 


14-0 


10-5 


111511 


12-0 


8-5 


A1787 


34-65 


38-15 


1115UF 


12-0 


8-5 


A1800 


31-65 


88*16 


1200U 


12-0 


8-5 


A 1800 A 


34-65 


:ss-i -i 


1200UF 


12-0 


8-5 


AIM!" 


:n -88 


38-15 


1229U 


12-0 


8-5 


AIS10A 


34-65 


38-15 


1236U 


120 


8-5 


A 19611 


:u-«ri 


38-15 


1238U 


120 


8-5 


A 1961 


34-65 


38-15 


1 UiOA 


120 


8-5 


A 1 962 V! 


S4-60 


88-18 


1 1271 


12-0 


8-5 


A.198S 


3-1-65 


88*16 


1437U 


12-0 


86 


A 196-1 


34-6. r , 


88-18 


1437UF 


12-0 


8-5 


A 1967 


31-65 


38-15 


1446U 


120 


8-5 


VIH67M 


M-ee 


:;<•];, 


1446U/45 


12-0 


8-5 


A 1963 


34-65 


38-15 


1458U 


31-65 


38-15 


A2160 


34-65 


38-15 


] I68f 


34-65 


:;s-l.-, 


A2161 


34 65 


3S-15 


1502U 


13-3 


9-8 


RC1413 


16-0 


19-5 


1700A 


13-4 


!l!l 


B01651 


16-0 


l»-5 


17201 


12-0 


8-6 


BT1251 


l'.l:.l . 


T.K.F. 


1726UF 


120 


8-5 


HT1410/8 


14-0 


10-5 


1746TJ 


120 


8-5 


BT14I0/L 


13-5 


10-0 


1746U/45 


120 


8-5 


BT1412 


16-0 


19-5 


1747U 


12 -ii 


8-5 


BT1651 


IC-ii 


19-5 


1748U 


12(1 


8-5 


BT1651 


16-0 


19-5 


1756U 


34-65 


38-15 


BX1752 


11-0 


10-5 


17571; 


34-65 


3815 


BT1 752C 


11-0 


10-5 


1768TI 


34-66 


38-15 


BT18408 


13-5 


10-0 


1768U 


31-65 


38-15 


BT1S40L 


13-5 


10-0 


1772U 


34-65 


38-15 


ST1497A 


34-65 


38-15 


I778U 


34-65 


38-15 


ST1800A 


34-66 


38-15 


17921 


34-65 


38-16 


1000 


M-HJ 


38-15 


17961 


34-65 


38-16 


1010 


34-65 


38-15 


1800 A 


13-4 


9-9 



° Dual diunrit-l I.F. strip, flu- 7 Mo * tor radio.) 



INTERMEDIATE FREQUENCIES 



213 





1 i.tion 


Sound 




Vision 


Sound 


MmM 


I.F. 


I.F. . 


Model 


I.F. 


I.F. 




(Mc/s) 


(Mcjs) 




(Mcja) 


(Mejs) 


PHILIPS (contd.) 

2i&r)i: 


84*88 


38-15 


PYE (contd.) 
BV20 


TB.F. 


T.R.F. 


2167U 


34-65 


88*18 ' 


BVSW 


T.R.F. ! 


T.K.F. 


2168TT 


34-65 


MS- 15 


BV21U 


T.K.F. 


T.R.F. 


2 1 U2 1 ' 


34-65 


38-15 


BV21BG 


T K.F. 


T R.F. 


2196U 


84*88 


88-18 


BV30 


T.KF 


T.R.F. 


2337A 


12-0 


6-5 


BV300 


T ll.F. 


T.R.F. 


2347A 


12-0 1 


8-5 


BV51 


T.R.F. 


T.R.F. 


602 7 A 


12-0 


8-5 


OS17 


3-1-65 


381 5 


C028T 


12-n 


8-5 I 


0S1TO 


31 05 


88*18 








US17UF 


34-65 


38-15 


PHOT 

CM 54 


13-6 1 


10-0 


CS17K 

OTL210V8 


34-65 
34-63 


38-15 
38-15 


CV34 • 


r.n.K. 


t.r.f. ! 


UTI/18F 


8448 


38*15 


( \ 35 


13-5 


inn 


(!TL5Srj 


31-65 


38-15 


OY7U 


i :•;•:, 


lii-u 


0TL6SVS 


34-65 


38-15 


CV77 


13-5 


10-O 


01314 


34-65 


38-15 


UV84 


13-:; 


9-8 


OTlflTl 


31-65 


38-15 


OV84/12 
OV87 


13-3 
13-3 


ii-8 
9-8 


CT.M17S 
OTM17/S 


34-65 
34-65 


33-15 

38- 15 


CV87/12 
DDC87 


13-3 1 
13-3 


9-8 
9-8 


CTMI7T 
0TM31 


31-05 

31-66 


38-15 
38-15 


DDC87/12 
1JUC97 


13-3 


9-8 


i TM2ICP 


34-65 


38-15 


84*88 


3S-15 


OTM21F 


34-65 


38-15 


DDC121 


34-65 


38-15 


CTM21/F 


31-65 


38-15 


TM54 


13-5 


10-0 


(T.M21S 


3-1-65 


38-10 


'L'V7ti 


13-5 


UM> 


OWI7 


34-65 


38-15 


TV.s l 


13-3 


9*8 


CW170 


31-65 


38-15 


TV84/12 
TV87 


13-3 
13-3 


8*8 

9-8 


GW17UF 
OW17GS 


34-65 
34-65 


38-15 
38-15 


TVS7/12 
TV*,i 1 


18-8 

34-65 


9*8 
38-15 


UW17F 
0W17S 


:;i-i;r, 
34-65 


38-15 
38-15 


TV 11 7 
TV107 


34-65 
34-65 


38-15 
38-15 


CW21F 
OW21S 
0Y58OV8 


.34-65 
3-1-85 


:;- - 1 5 
88*18 


TV 11 OF 


34-05 


38-15 


34-65 


38-15 


TV111 


64-66 


88*18 


1316T 


T.K.F. 


T.R.F. 


■|'V1 17 


34-65 


88-18 


D18T 


T.K.F. 


T.K.F. 


TV 120 


84*88 


88-16 


DI8T/F 


T.K.F. 


T.K.F 


VS9f» 


T.R.F. 


T.K.F. 


FV1 
F\ 'li' 


35-D 
35-0 


38-5 

38-5 








FV20 


35-0 


38-5 


PORTADYHE 






FV40 


35-0 


38-5 


QA17 


31-5 


38-0 


FV4CDI. 


35-0 


38-5 


■[■758 


84*8 


38-0 


LB17KF 


31-65 


381 B 


TA17 


34-5 


38-n 


LV20 


T.K.F. 


T.R.F. 


TC12L 


14-0 


10-5 


1.V21G 


T.R.F. 


T.K.y. 


TC12M 


14-0 


10-5 


LV21HG 


T.K.F. 


T.R.F. 


TT126 


16-0 


19-5 


LV30 


T.E.F. 


T.R.F. 


TV237 


34-5 


380 


LV30C 


T.R.F. 


T.R.F. 


TV517 


Hi-" 


19-5 


LV51 


T.K.F. 


T.R.F. 


179 


34-5 


38-0 


I'VllU 


34-65 


33-15 


617 


16-0 


19-5 


RTL17 


34-65 


38-15 








S1'17 


34-65 


38-15 


PYE 

PTY 






Sl-17l.lt 


34-65 


38-15 


34-65 


38-15 


V2 


16-11 


19-5 


H16T 


T.E.F. 


T.K.K. 


| V4 


|C-(I 


19-5 


l'.l>T 


T.R.F. 


■ T.R.F. 


1 V4C 


16-0 


19-5 


B18T/F 


1 TR.F. 


T.K.F. 

1 


V7 


lfi-0 


111-5 



214 



TELEVISION ENGINEERS* POCKET BOOK 





Vision 


Sound 




Vitim 


SuHltd 


Model 


I.F. 


I.l\ 


Model 


i.r. 


i.r. 




(Mc/s) 


(J/c/s) 




(Mcjs) 


(Mc/s) 


PYE (contd.) 






R.G.D. (contd.) 






V7« 1. 


160 


19-5 


1,33511 


13-0 


9-5 


V70DL 


16-0 


19-5 


L235I 


T.R.F. 


T.R.F. 


V14 


34-65 


38- IS 


L27.il 


13-0 


9-5 


V14C 


3465 


38-15 


T14 


34-65 


38-15 


V17RG Trio 


31-65 


38-15 


1 179 


13-0 


9-5 


V17HM 


34-65 


38-15 


1 lyii 


13-0 


9-5 


V110 


34-65 


38-15 


189 


18-0 


9-5 


V200 


84- es 


38-15 


lilfp 


i::u 


95 


V200LB 


84*68 


38-15 


502 


::4-t;.-. 


88*15 


V III ill F 


34-65 


38-15 


etm 


84*66 


3S-1.1 


V30US 


34*66 


38-15 


800 


:i4-»>r. 


3815 


V310F 


34-65 


88-16 


605 


34-65 


38-15 


V310S 


34*68 


38-15 


1455T 


l«-0 


19-5 


V4Q0 


84*66 


:ts-ir, 


L466T 


16-0 


19-5 


V09 


160 


19-5 


17550 


16-0 


19-6 


VT2 


160 


19-5 


it.,., r 


16-0 


19-5 


VT4 


34-65 


38-15 


17560 


16-0 


l'J-5 


VT7 


10-0 


19-5 


] 75(11 


160 


19-5 


VT70B 


w-o 


19-5 


17670 


160 


19-5 


VT70DL 


16-u 


19-5 


1800 


13-11 


9-5 


VT17 


34-05 


38-15 


8849T 


13*0 


9-5 


VTI7(J1> 


34-65 


38-15 


6012T 


14*0 


In-.-. 


"VT170UL 


:u-«5 


38-15 


6014T* 


1 i-n 


|n-7. 


VT210 


34*65 


38-15 


6014/3T 


31-H 


:,;■:, 


VT21CJJ 


34-65 


38-15 


■■nl.Vl 


14-0 


10-8 


17'RJDL 


34 -65 


38-15 


6U17T 


110 


10*8 


815 


T.R.F. 


T.K.F. 


8017/tT 


34-0 


37-5 


816 


T.R.F. 


T.ll.K. 


7016T 


14*0 


10-5 


817 


T.R.F. 


T.K.F. 


70181 


14-0 


10-5 


Sl!l 


T.R.F. 


T.R.F. 


70170* 


14-0 


10-5 


828 


T.R.F. 


T.H.I . 


7017/30 


34 


37-6 


SSip 


•VMM, 


T.K.F. 








838 


T.K.F. 


T.R.F. 


RAYMOND 






843 


T.K.F. 


T.K.F. 


F1U 


T.H.K. 


T.K.F. 


4045 


T.R.F. 


T.11.F. 


FliiK 


T.lt.F. 


T.U.I'. 


4046 


T.R.F. 


T.i :.K. 


F.->:; 


in-r, 


10-0 








F53R 


11-11 


10-5 


R.G.D. 






PS4B 


11-0 


10*8 


" Dug 17 '* 


31-65 


88-18 


F56 


84*78 


38-25 


l>er|i 17A 


::■■•■,;. 


68*18 


Fiin 


31-75 


88*38 


Deep 170 A 


34 65 


88-18 


F79P ' b J 


84-78 


38-26 


" The 17 " 


16-0 


Hi-fi 


84*78 


38-25 


•' Tins 21 " 


31-65 


38-15 


F7HF r 


84*78 


38-25 


Iil7"'0 


i:i-ii 


9-5 


!•:<:: 


34-75 


38-25 


IUSi-0 


18-0 


9-5 


F100 


31 -75 


38-25 


»as.V) 


13-0 


9-5 


ii'xh 


31-75 


3S-i5 


B2351 


130 


9-0 


1*10*1 


-.4-7.-1 


:;-■>:. 


B2351T 


13-U 


9-5 


Flu;. 


34-75 


38-25 


i«;.>i 


13-0 


9-5 


Flu:. I 


84*78 


88*38 


054* 


14-0 


10-5 


Fli>7 


3 1- 75 


38-25 


OSS 


16-0 


19-5 








HI 700 


13-0 


9-5 


REGENTONE 






11181 10 


130 


9-5 


Rig 12: Oh. 1 


1 :;■.-, 


10-0 


H235I 


i:;n 


B-5 


Oh, 1 


lKi 


10-5 


1,1700 


18*0 


9-6 


Big 1211 


14-ft 


Hi-,", 


LI 800 


13-u 


9-5 


Big 121T 


140 


10-5 



• In some special arena, vision is 15-0 Mc/s and 1 1-5 Mc/b sound. 



INTERMEDIATE FREQUENCIES 



215 





Vision 


Sound 




Vision , 


Snltml 


Model 


i.r. 


I.F. 


Model 


i.r. | 


i.r. 




(Mcfs) 


(Mcjs) 




(Mcjt) 


(Me/t) 


REGENTONE (eontd.) 






SOBELL (contd.) 






Big 12L 


Fin 


10-5 


11 81 


18*0 


9-5 1 


Big 12/6 


14*0 


10-5 


T122 


13-0 


9-5] 


Uig 15/5 


i ■.,, 


10-5 


T143 


ir,-u 


19-5 


Big 15/6C 


li -I 


in--, 


T1430 


16-0 


19-5 


T15B 


14-0 


lii.?i 


Till 


16-0 


19-5 


T16H 


14-0 


10-5 


TM5 


34-5 


380 


T15K. 


140 


10*8 


IT 71 


16-0 


19-5 


! 151, 


13-5 


10-0 


IT 7 10 


16-0 


19-5 


Tlu ilk. 2K 


14-0 


10-5 


T172 


34-65 


38-15 


T15Mk. 211 


11-n 


10-5 


T174 


10-0 


19-5 


TIC Mk. 2L 


14*0 


10-5 


T174C 


10-O 


19-5 


T21 


34-05 


38-15 


TT7LLC 


16-n 


19-5 


T2-1FM 


:;ir.:. 


38-15 


T175 


34-5 


38-0 


121 Mk 11 


84-88 


38-15 


T1750 


34-5 


88*0 


T176 


34-65 


38-15 


T17SI,0 


34*6 


38-0 


TI77 


:.!..;:, 


38-15 


T170 


34-05 


38-15 


TKN-I 


B4-6S 


::> t8 


T176C 


34-65 


38-15 


TEX-.'. 


84*88 


88*18 


T176I-C 


3405 


38-13 


TEN-8 


34-65 


38-15 


Tl 78 


34-65 


38-15 


TEN-12 


34-65 


38-15 


T17 


34-05 


38-15 


TU2UH 


13-5 


10-0 


TliU 


84*88 


88*18 


TH20L 


13-5 


10-0 


T224 


16-0 


19-5 


TK177 


3-1-65 


38-15 


T225 


16-0 


10-5 


TT7 


16-0 


18-8 


T227 


16-0 


19-5 


14T° 


140 


10-5 


T274 


10-0 


19-5 


170° 


14-0 


10-5 


r J'27 7 


18-0 


19-5 


1 700MB ° 


140 


10-5 


T27S 


84*88 


38-15 


17T «* 


11-n 


10-5 


l-.'-.'-J 


34-05 


38-15 


1480 


310 


37-5 


T340 


16-0 


19-5 


143T 


34-0 


37-5 


T317 


16-U 


19-& 


153T 


310 


:;;-:■ 


T848 


34-65 


3S-17. 


153XT 


34-0 


37-5 


T1291 


13-5 


10-0 1 


173C 


84*0 


37-5 


TPSI47 


34-65 


38-15 


17 3COM 11 


84*0 


37-5 


•EPS147DL 


34-05 


88*18 


I73T 


84-0 


87*8 


TFS17:; 


:;!■.;:, 


38-15 


17 IT 


I-;-. 


19-5 


'ITS181I 


34-65 


38-15 


1S3T 


84*0 


:;;■:. 


IP8187 


34-65 


38-15 


8170 


34 -0 


37-5 


TBG174 


16-n 


19-5 


817*1 


34-0 


37-5 


TUU.175 


34-5 


38-0 








T8148 


Iti-u 


19-5 


SOBELL 






3S17 


16-0 


19-5 


SCtM 


84*88 


38- U 








.~l27n 


34-05 


38- 1 8 


SPENCER-WEST 






rti 


Hi- II 


19-6 


'IV.-w- 


:;i-t;.-, 


38-15 


'l'2H' 


Hi -ii 


l'J-5 


TV17 


84*88 


3S-15 


T21L0 


16-0 


19*6 


r\ it:iu 


34-65 


88*18 


T22 


34-65 


38-15 


TV 958 


84-88 


38-15 


T23 


34-65 


38-15 


17 


34-65 


38-15 


T2I 


84-88 


3S.]5 


171 


34-65 


38-15 


T87 • 


T.U.F. 


T.U.F. 


172 


34.«.-i 


38-16 


T89L 


T.R.F. 


T.K.F. 


173H 


34.65 


38-15 


T90 


13-0 


9-5 


174 


34-65 


38-15 


T81 


13-0 


9-5 


175 


34-65 


38-15 


Tl')7» 


T.K.F. 


T.R.F. 


176 


34-65 


38-15 


T120 


13-5 


mot 


178 


34-65 


38-15 



• Or 15-0 Mc/s vision and 11*5 Mc/s sound. 

i 14 Me s viii'imi uinl hi 5 Mi:_'s sound Un Birtaingbttm models. 



216 



TELEVISION ENGINEERS' POCKET BOOK 





VUhm 


.SMI !lll 




Vision 


Sound 


Model 


l.F. 


l.F. 


Model 


l.F. 


t LI-'. 




(Me/*) 


(Sfefs) 




(Mejs) 


| (J/c/,0 


SPENCER- WEST << ■- 


id.) 




ULTRA (contd.) 






ISO 


;;i ■(',:, 


sg*is 


V84 series: 






181 


34-65 


3815 


Oh. 1, 2, 4, 5 


19-5 


10-0 


957 


31-65 


38-15 


Ch. 3 


18-0 


14'5 


808 


34-05 


S8-1C 


VA72 series: 












Ch. 1. 2, 4, 5 


19-5 


16-n 


STELLA 






Ch. 3 


18-0 


14-5 


STUBOtl 


13-4 


9-9 


VE'14-53 


34-65 


38-15 


STI481A 


12-0 


8-5 


\ 1*17 72 


84-68 


38-15 


&T1S00U 


12-0 


8-5 


\ 1 '2 1-72 


34-65 


38-15 


OT15220 


13-4 


9-8 


\ 1117-52 


34-65 


38-15 


9T871TO 


34-05 


38-15 


\ 1:17-62 


34-65 


:;s-ir. 


3TS781U 


84-88 


38-15° 


S 1(17-71 


34-65 


38-15 % 


sTetiin 


}-j.,, 


8-5 


VR21-71 


84-89 


38-15 J 


STG 1 1 t i IT, 


12-LJ 


8-5 


VT8-14 


34-5 


3841 


ST6417U 


12-0 


>-.-> 


vi'g-ie 


.14-5 


38-0 


ST0417U/4& 


12-0 


8-6 


VT9-15 


34-0 


38-0 


t-regnu 


34-65 


38 15 • 


VT9-17 


84-6 


38-U 


S'reoair 


34-eri 


38-15 6 


W8-17 


34-5 


18-8 


.ST8314U 


ISO 


8-5 


W17-89 


:; i -,-, 


38-U 


STSSHUir 


12-0 


8-5 


w 21-eo 


34-5 


38-0 


sisiiin 


12-0 


8-G 


W47 series f 


10-7 


7-2 


8T8814TJ 


84-68 


8848 


W57 series f 


10-7 


7-2 


ST8517U 


84*88 


8846 


W70 scries 


19-5 


10-0 


8M81TO 


84-88 


8B-1*« 


W 72 series 


19-5 


16-0 


ST86211T 


:;i ■(■,:, 


88*18 « 


W80 series: 






ATR9I711 


:s4-(;ri 


8t*18« 


Ch. 1, 2, 4, 5 


19-5 


16-0 


- ! s:i21T 


34-65 


88*18 « 


i h, 8 


18-0 


14-5 


SX0S12H 


12-0 


8-5 


\\'S-l BOta! 












Ch. 1, 2, 4, 5 


19-5 


16-0 


STRAD 








18-0 


14-5 


RMT717 


18*0 


19-5 


W811 


34-5 


38-0 








WB17-58 


84-88 


38-1 r. 


ULTRA 






W III 7-62 


:;i ■(;.-, 


:;v-i;, 


It") 7 aeries j 


10*7 


7-2 


WB31 88 


:;m;:, 


3H 15 


D70 series 


18-8 


16-U 


WT9-17 


84-8 


88-0 


T22 


8-8 


2-3 


Y72 series 


19-r. 


Ki-u 


T24 


5-8 


34 


Y73 Si-lies 


19-5 


16-0 


Vs. 11 


M*8 


88-0 


T84 series: 






VS-IO 


34-6 


38-fl 


Ch. 1, 2. 4, 5 


19-5 


16-0 


V8-1 7 


34-5 


38-U 


Ch. 3 


18-n 


14-5 


VI 4-53 


84-88 


38- IS 


YA72 series: 






VI 5-80 


34-5 


88-0 


Oh. 1, 2, 4, 5 


19-5 


16-0 


VI 7 60£ 


:;■!-. i:. 


88-11! 


i 1.. ::. 


13-0 


14-5 


517-50B 


34-65 


88-15 


YA73 series: 






V17-WI 


31-5 


33-0 


Oh. 1, 2, 4, 5 


19-5 


16-0 


VI 7-63 


:m-g:i 


38-15 


Ch. 3 


18-U 


14-5 


VI 7-70 


M<60 


38-15 1 


"> B7B series: 






V21 70 


84-88 


38-15 1 


Oh. 1, 2, 4, 5 


19-5 


16-U 


V it series t 


111-5 


16-0 


Ch. 3 


18-0 


1 1-5 


V60 series 


19-5 


16-0 1 








V71 series 


19-5 


16-0 | 


VIDOR 






V80 aerlea : 




■ 


i mw9 


13-0 


9-5 


Ch. ], 2,4, 5 


19-5 


100 i 


ON389A 


13-1 


9-6 


Oh. S 


18-(J 


14-5 


CN370 


9-75 


0-25 



* Sound I.F.T.s tuned to 38-35 Me/s. 

t Loudon models uiij-ned to upper stdebaad. 

I F.M. suh-miit 1(1-7 Mc/s. 



INTERMEDIATE FREQUENCIES 



217 





Vision 


Sound 




Vision 


Sound 


Model 


l.F. 


l.F. 


Vodd 


l.F. 


l.i-. 




(Jfc/») 


(Me:*) 




< Me *) 


(Mc}s) 


VIDOR (contd.) 






VIDOR (fonttl.) 






OH877 


9-75 


0-25 


084888 


16-0 


19-5 


0X390 


8*7* 


0-25 


CN4220 


16-0 


19-5 


CN391 


9-75 


6-25 


CK4298 


Ki-0 


19-5 


(■N4nr» 


9-76 


6-25 


l.'K4229 


19-0 


19-5 


0N408 


9-75 


6-25 


0374880 


34-65 


38-15 


ON4201 


9-75 


6-25 


OM4231 


34-65 


38-15 


CN4202 


9-76 


6-25 








CN4206 


9-75 


0-25 








ON4807 


!i-75 


6-25 


WHITE 1BBOTSON 






UN420S 


9-75 


6-25 


Murk 1 


14 


10-5 


ON4209 


9-75 


6-25 


Mark 8 


14-0 


RI-5 


(1N4212 


9-75 


6-25 


1612: Ch. 1,2, 1 


14*0 


10-6 


CX4213 


L8-0 


111-5 


1 lb. 3, 5 


18*88 


11-78 


0N4818 


16-0 


19-5 


2010: Ch. 1, 2,4 


14-0 


10-0 


CN4216 


10-U 


19-5 


Oh. 3, 5 


Ij-M 


11-75 


<M217 


16-rj 


19-8 


2418: Oh. 1,2, 1, 5 


14 


10-5 


(NI218 


10-0 


19-5 


Ob. B 


15-25 


11-75 


CN422U 


100 


111 -5 


4830: Ch. 1, 2, 4 


14 


10-5 


ON 4221 


16-0 


J 9-5 


Ob. 3,5 


15*25 


11-75 



Notti Intermediate heQtteaoJea wo now Hsner&lrj* 84*85 Me a (virion) and 88*18 
tlofs (sound). Where, aa Known in the Table, ttuaadaefoutm huve adopted these 

ireijui-ueir-^. ilesiii iisiimIIv lie iL-siirue.1 lli:it lln'M-will be re(:iiiicil [Of Inter liioiicls. 



Switch Tuner Alignment 

Tho tuner should be connected as sot out for the turret tuner. 

For setting iIh- nsrilhit.ur, start- at Channel 13 and work clown 
the coils to Channel I . 

If one eoil does not have enough adjustment, it will he necessary 
lo return to (channel 13 (for Band II T) or Channel ;") (for Band 1) 
and make a new atari. 

Tho anode, R.F. anodo and mixer grid circuits should he 
commenced at Channel 13 by adjusting L9, Lll and L27 (Fig. 
7) for tho best curve shape. 



Fir,. IS. — PORT4BLB RXSOTKB 
TxsntB Moiiki. OT888/8, 

This equipment emnl-ii 
wide-r*iiifjc signal (renerator(70 
ke/s to 70 MC/S) with itiU-rn;il 
:uul estx-rtial iinailituile moilulsi- 
tiuu, a tone aooroa <>I WMrlable 
level rod :u i ;iinlii)-i'ri.'i]iieuo.v 
power meter, in a oonipaei 
itsaembly. 

{Mari-oiii Instruments l-td.) 




218 



TELEVISION ENGINEERS* POCKET BOOK 



Now tune down to Channel and, if the curve is unsatisfactory, 
adjust C7, C12. Repent until Channels 6-13 inclusive are 
satisfactory. 

Now set up Channel 5 with L7, LI 3 and L22. Cheek channels 
5-1. If unsatisfactory, it will be necessary to pinch up or 
stretch out the little coils round the periphery of the switch 
wafers until the curve is correct. When this* is done always 
check the channels below the one adjusted. 

Always set up the aerial circuit for maximum gain at. the 
mid- f re q u o ncy . 

The A.G.C.' lead from the R.F. Grid should be earthed if no 
contrary instructions are stated. 

Miscellaneous Information 

A further point in the use of a sweep generator is that it may bo 
possible to see the response of the tuned circuits individually in 

330A 

WMA< 



GERMANIUM DIODE 

+ 



bf/if 

CHOKE 



TO OSCILLOSCOPE 



Pig. 13.— anode Damping ijkvick. 

case of need. To do this, connect a detector made up compact lv 
to the circuit of Fig. 13 to the anode of tho valve following the 
circuit under test and connect the wohbulator to the preceding 
grid. 



[SECTION 14] 

CATHODE-RAY TUBES 

by A. G. Thomson, B,Se.(Eng.), A.M.I.E.E, 

At one stage, almost nil cathode-ray tubes used in television 
receivers employed magnetic deflection and focusing of the 
electron brain. In recent, years, however, there has been a trend 
towards electrostatic focusing, fehtxa eliminating the external 
magnets and making the tube easier to set up. 

KIl'. 1 shows the arrangement of a tetrode tube with magnetic 
focusing. Electrons are emitted by the indirectly-heated 
cathode K and are attracted by the first anode A lf which is 
usually 1 50-3OO V positive with respect to tho cathode. Aj 
consists of a skirted disc with a small central hole through which 
most of the oloctrons pass up tho tube to strike the fluorescent 
screen S, which is composed of i; phosphors " that emit light. 
under electron impact {e.g., zinc sulphide, blue ; or zinc cadmium 
sulphide, yellow). To obtain an approximation to white light. 
mixtures of phosphors are often used. Surrounding the cathode 
is tho cup-shaped grid G, also with a small central hole. An 
electric field is produced between grid and cathode by virtue of 
i heir potential-difference, and this controls tho number of elec- 
trons drawn through the first anode — and hence the brightness of 
the spot. A grid voltage 2.1 100 V negative to cathode will cut 
off the electron flow altogether. The second anode. A... eon- 




l-n:. 1.— AltllAXaBMKNT OF A TYl'lCAI, TBTROOB CATHODE-RAY TUUK. 

219 



220 TELEVISION ENGINEERS' POCKET BOOK 




Pia. 2,— FocuaiNa by Short Coil. 
(e) Shows an end view of the electron path. 

neeted internally to the graphite coating C inside tho wall, gives 
further acceleration and governs the final electron velocity : its 
voltage is 6-16 kV (20-50 kV in projection models), determining 
the ultimate possible brightness of the screen fluorescence. 

Focusing 

The electrons, travelling at high velocity, must be focused to a 
small spot, e.g., 25 thousandths of an inch in diameter on a 14-in. 
tube. Now a flow of electrons, whether in a wire or not, is a 
current; and when a current flows across a magnetic field, it 
experiences a forco which tends to move it. In the cathode-ray 
tube the electron stream thus experiences the deflecting force 
when passing across a magnetic field. By means of a short coil, 
or a permanent-magnet arrangement, a field, as shown in Fig. 
2 (a), is produced. Electrons passing along the tube axis do 
not cross this field, and so are unaffected, but those entering at 
P are deflected into a helical path whose radius is proportional 
to the strength of tho field, and whoso pitch is proportional to the 
tangential velocity of the electrons. Since the axial velocity is not 
affected by the magnetic field, all electrons may be brought to a 
focus on the screen in a spot corresponding to tho origin— the 
cathode. It is thus important for the cathode to be small so that 
the focused spot is well defined. 

Deflection 

Tho spot must bo made to transverse tho screen rapidly from 
side to side and more slowly from top to bottom to produce the 
" raster ". For line scanning a varying magnetic field is re- 
quired which varies linearly to deflect tho spot left-to-right and 
then rapidly right-to-left. Simultaneously, there must be a 



CATHODE- RAY TUBES 



221 



corresponding top-to-bottom and return motion for frames. 
D.C in Fig 1, shows the deflecting coils : the deflection is at 
right angles to the direction of the magnetic field, so that tho 
vertically-disposed field is that of the line-deflection coils. In 
this way the spot will trace out the " raster '*, which corresponds 
to the pattern traced by the camera tube. 

Modulation 

To reproduce the " picture " as seen by the camera, the 
instantaneous brightness of the spot is modulated by the instan- 
taneous variation of the cathode-grid potential from its mean 
or quiescent value, determined by the " brilliance " control. 
This may be done either by driving the grid positive with respect 
to the cathode, or by applying a negative-going signal to the 
cathode. 

Ions 

In addition to the electrons, positively and negatively charged 
ions are also produced tn the cathode-ray tube. The former are 
attracted to the grid and cathode, but the latter travel to the 
fluorescent screen. They are between 5,000 and 500,000 times 
heavier than electrons, and though like electrons they are attracted 
by the first and second anodes, they are much loss deflected by 
magnetic fields. Tho deflection of electric particles by a magnetic 
field is directly proportional to the Btrength and the length of the 
deflecting field and its distance from the screen, and inversely 
proportional to the particle velocity. But the latter varies as 
tho square root of the quotient of the final anode voltage and 
particle mass : hence the heavy negative ions are less deflected, 
and they destroy the fluorescent property of the screen by 
bombardment over a small central area. Tho result is a dark 
spot referred to as " ion-burn ". Ion-burn may be avoided by 
removing the ions from tho beam, either by passing the beam 
through an olectrical and then a magnetic field so that the ions 
are deflected in tho first and not in tho second (see Fig. 3) or by a 
" bent-gun " in which the beam is initially projected at about. 
10" to tho tube axis and an " ion-trap " magnet deflects the elec- 
trons back to the tube axis. Tho ions, however, carry nearly 
straight on to the second anode (see Fig, 4). 

ION TRAP 
MAGNET 



KlO. 3.—" USDKKLECTKU 

Buam " Typk of ion Trap. 




222 TELEVISION ENGINEERS' POCKET BOOK 



ION TRAP 
MAGNET 
G i A 2 



Fio. 4.—" hent-ous " El it 
op Ion Tkap. 



is 



5^~ 



n 



K A, 

A different treatment of the problem is to prevent the ions in 
the beam from reaching the fluorescent material by backing 
it with a very thin metallic film. Aluminium is the usual metal, 
and considerable success in reducing ion -burn has attended 
" aluminising ", which was originally introduced mainly to 
improve brightness and contrast. In somo modern tubes both 
methods of reducing ion- burn are used. 

Because of the thinner stem used to reduce i lie power needed 
in the (lellecl ioii coils, bent-gun ion traps are not tilted in I Ml 
deflection tubes, nnd these are usually aluminium hacked, 

Arnminising 

In a non-backod tubo about half tho light is visible at the front 
of the phosphor. The remainder appears at the back, and ovon 
with an internal graphite coating some of this light is reflected 
back to tho screen, where it roduces contrast by faintly illumina- 
ting the whole screen. With aluminising, the useful output is 
increased, as the aluminium film reflects the backward output, 
improving both brightness and contrast. For maximum 
efficiency the thickness of the aluminising film is closely related 
to tho final E.H.T. voltage, so that tho indiscriminate fitting of 
an aluminiscd tube may not result in any noticeable improvement 
in performance. 

Tinted Screens 

Dark- or tinted -glass scroens have also been introduced tc 
improve picture contrast when viewing in strong ambient light. 
Ambient light illuminates the " black " portions of the screen 
and reduces contrast. With tinting, the small loss of brightness 
(as the phosphor is seon through the tinted glass) is compensated 
by increasing the brilliance control. Tho "black-level" seen 
by the viewer is determined by the ambient light reflected from 
the screen, and as this has to pass through the tinted glass twice 
(once to reach the phosphor and once to reach the viewer) the 
result is a darker *' black " and improved contrast. A.G.T, 



CATHODE-RAY TUBES 



223 



Multi-electrode Guns and Electrostatic Focusing 

The guns in most early picture tubes were of either triode or 
tetrode design, but recently pentode, hexodo and heptodo types 
have also become popular. These offer the advantage that a 
small"!- beam diameter can ho produce! hi '!"' region of the 
deflection coils, making for more uniform focusing over flic entire 
area of tho screen. In earlier tubes there was often a tendency 
towards " deflection defocusing " at tho edges of the screen. 

Another change of considerable importance is the introduction 
of electrostatically focused tubes, in place of permanent-magnet 
or electromagnetic focusing. The electrostatically-focused tube 
not only eliminates the focus magnet, with its problems of 
adjustment and mounting, but also reduces assembly and 
setting-up time. It also means that a potentiometer-type focus 
control can be fitted, but, as this method of focusing seldom 
requires subsequent readjustment, it is sometimes referred to as 
" auto focus M and is adjusted by altering the connection of the 
focusing electrode to the tube base, permitting a choice between 
the fixed potentials represented by "chassis", the normal H.T. 
lino and t\m " boosted H.T." line;. 

Wide-angle Deflection Tubes 

The length of i lie picture tube is the main factor in determining 
the depth of the receiver cabinet, and considerable reduction in 
cabinet size for a given size of picture has been made possible by 
increasing the deflection angle of the electron beam. In earl\ 
tubes this angle was often about 60°, requiring a long bulbous 
section of tube, but the angle has been progressively increased, 
lit st to about 70°, then to S)0" and most recently to 110°. The 
overall length of a modern 21-in, tube is thus less than I hat of an 
early 9-in. tube. 

The main disadvantage of tho wide-angle deflection tube is 
the greater scanning power required, although increases in tho 
i lliciency of scanning components and new circuit techniques 
can provide the extra power without unduly adding to the 
power dissipation of the time- bases. 



a a, aj 



■iu_J_C 



-"I 



* 3 



T 



DEFLECTOR COILS 




Tvi'KAi. 'IViik l sim; BLKCTEOSTATIC Foci sim;. 



224 



TELEVISION ENGINEERS' POCKET BOOK 



CATHODE-RAY TUBES 



225 



One means of making a given amount of scan power more 
effective is to place the deflection coils nearer to the electron beam, 
and the necks of 110° tubes are narrower than for earlier tubes, 
For this reason, these tubes have a smaller eight-pin base, known 
as the B8H. Since these pins are more readily damaged lima 
with B12A bases, cure should be taken when removing Or replacing 
the socket. 

With 110'" lubes, which arc usually more rounded than the 
smaller-deflect ion-angle types, it. is common practice to fit a 5 : 4 
!is|iec,t ratio mask, and then to set up the receiver with sou if 
horizontal overscan. 

Handling Cathode-ray Tubes 

Although the danger of implosion when handling tubes is 
relatively slight, provided that core is taken not to let tho neck 
strike tho chassis or service bench, it can occur, and it is advised 
that precautions to guard against the effects of such an implosion 
should always bo taken. The high vacuum of tubes means that 
the pressure mi the envelope is ver\ high, amounting bo more 
than a ton for relatively small tubes. When a tube is dropped 
or comes into sharp contact with some other object, the gloss 
may shatter, and be spread in all directions at high velocity. 
It is therefore highly advisable to wear gloves at all times when 
handling tubes, while protective goggles will give an added sense 
of security. 

The tube should always bo lifted and carried by placing one 
hand beneath the face, this hand taking the weight and fulfilling 
tho lifting action. Tho other hand should be placed on tho 
flare to steady the tube. This avoids placing any strain on the 
junction between tho cone and the neck, which is mechanically 
tho weakest part of the tube. With metal-cone tubes, tho 
supporting hand must be beneath the face and not merely 
hooked under the lip, aa this would impose a strain between the 
glass face and the metal emir. 

The tube must never bo placed face downwards on tho bare 
surface of a bench, as this is likely to cause scratches which will 
mar the picture. It is best to place tho tube on a piece of felt 
or other thick material, or, failing this, a few sheets of paper. 

The risk of implosion is greatly increased if the glass surface 
is scratched or if the rim of a metal cone is knocked. It should 
also be remembered that tho internal and external coatings 
of many tubes form a condenser, and if tho tube is handled 
when this is in a charged condition, it is possible to receive a shock 
sufficiently strong to induce the recipient to drop the tube; 
this risk can be eliminated by always connecting the final anode 
to the external coating when the tube is removed from its socket. 
Also, to touch this coating with damp hands will impair its 
insulating properties. 

Viewers should be protected from implosion by a strong glass 
or plastic screen : suitable screens include {-b\. armour-plate 
glass (not ordinary plate glass) or -fc- in. -thick fiat perspex sheet. 






In time, a film of dust will bo formed on the face of the tube by 
electrostatic attraction. This can bo removed by wiping with a 
soft, slightly moistened cloth, after which it must be dried 
thoroughly. Anti -static preparations may be used, but the 
makers* instructions should be carefully followed. 

When refitting, never use force when inserting the tube into 
the deflection yoke and focus coil, and take care not to tighten 
the tube straps and clamps excessively : remember that while 
this might not by itself cause the tube to break, a tube subjected 
to excessive clamp pres s ure is much more liable to break should it 
bo accidentally struck. 

Replacing Cathode-ray Tubes 

One result of tho rapid development of television picture- 
tube technique has been the multiplicity of types used during 
the past few years; it also raises tho question of replacing 
the older types of tubes, when they wear out, by more modern 
designs. In particular, the service engineer is frequently 
called upon to deride whether h is advisable la replace the 
original tube with one fitted with an ion trap. In general, tho 
following questions must be answered before a decision can be 
made : 

(1) Is there sufficient space for the ion-trap magnet ? 

(2) Are there any iron parts close to the cathode-ray tube 
that may affect the field of tho ion trap ? 

Two other factors also have to be taken into account when 
substituting now types of cathode-ray tubes. Many current 
tubes have their external surface coated with Aquadag, which 
is intended to form part of the E.H.T. smoothing filter. If a 
non-coated tube is replaced by a coated tube, it is essential 
that the coating be connected to chassis ; otherwise the coating 
will attain a high positive charge and be a source of danger. 
Difficulty may also occasionally be experienced in fitting a new 
tube in an old-typo mask ; this is because new production 
methods result in there being a slight difference in the finish of 
the cathode-ray tube where the face and flare meet. 

PICTURE-TUBE SALVAGE 

The replacement of a picture tubo represents a considerable 
item of expenditure to the average owner, and service engineers 
are often asked if they can avoid the need to purchase a new 
tube, even at some cost to picture quality. 

Makeshift repairs are often inadvisable, as any temporary 
improvement may soon be reversed, with the result that a new 
tube has to be purchosod after all, and money spent on extending 
the life of the original tube will have been wasted. There are. 
nevertheless, several methods of picture-tube salvage which 
have become fairly well established in practice, and often give 
reasonably satisfactory results for a worth-while period. 



226 TELEVISION ENGINEERS * FOCKET BOOK 

Low-emission Tabes 

Where the picture has become " fuzzy " with little contrast 
or brilliance and with a tendency to turn negative when either of 
these controls is advanced, this is often a sign of low emission. 
Tun i net hud- of Ictnporarj rejuvenation of tin- cathode emission, 
provided that the tube is still " hard ", are fairly widely used, 
although in both systems it should he clearly recognised that there 
is thp risk of the attempted " cure " causing the complete break- 
down of the heater. 

The first is to run the tube for a short period with the heater 
considerably over-run and with all other voltages removed 
(sometimes a potential of about 100 volts is put on the grid), by 
means of a tapped transformer or auto-transformer. The other 
method, which is probably more widely used, is to install a 
permanent " boost " transformer or auto-transformer providing 
from 20 to 50 per cent additional heater voltage. The installation 
of a boost transformer has frequently extended the useful life of 
tubes by many months, particularly' with the older type of low- 
voltage heater, although in other cases the life may be prolonged 
for only a short period; the extra life averages roughly about 
four to six months. 

Electrode Short-circuits and Miscellaneous Faults 

Heater-cathode short-circuits, often of an intermittent nature, 
are not infrequent, and may result in flashing, uncontrollable 
brilliance, hum bars or absence of raster. Where a heater- 
cathode short-circuit has been traced, isolating transformers, 
which are specially made for this application and which are now 
readily available, provide a means of extending the useful life 
of the tube. Such transformers must have a very low inter- 
winding capacitance, as otherwise (hare will be considerable loss 
nl' high-frequency video signals (which, with the heater-cathode 
short-circuit, will appear on the heater line) and hence deteriora- 
tion of picture quality. The use of an isolating transformer is, 
of course, practicable only on A.C. mains. With the aid of an 
isolating transformer, tubes with heater-cathode short-circuits 
can often be used quite successfully for relatively long periods; 
in fact, there is little evidence that the life of a defective tube 
fitted with an isolating transformer differs appreciably from that 
of a normal tube. 

Similar fault symptoms may sometimes bo traced to grid- 
cathode short-circuits. Where' the tube has a totrode gun, it is 
possible, though often at some cost to picture quality, to strap 
the grid to the cathode and then to rewire the tube with the 
first anode acting us control grid. 

Intermittent inter-electrode short-circuits often occur only 
when the tube is at full operating temperature and can sometimes 
bo eliminated by slightly lowering the heater voltage ; a simple 
method with series-connected tubes is to wire a suitable rosistor 
in parallel with the heater of the tube. 



CATHODE-RAY TUBES 



227 






It is worth noting that premature tube failures and inter- 
electrode short-circuits are frequently caused by the over-running 
of the heater and consequent high cathode temperature. It is 
recommended, when replacing a faulty tube, to check the heater 
voltage in a parallel -fed receiver and to check the heater current 
in a Beries-fed receiver. Measurements should bo made after 
checking that the mains- tapping is correctly adjusted. Currents 
should be within o per cent of the rated figure and voltages 
within 7 per cent. 

A picture-tube fault that may occasionally develop in fairly 
new tubes is a change in the grid cut-off characteristics; this 
may result in excessive brilliance even with the brilliance control 
set ii t minimum. This type of fault can sometimes be overcome 
I iy adjusting bias levels; sometimes by simply connecting a high- 
value resistor {e.gf., 10M) between the first anode and chassis. 

Scratched tube faces can often be repolished by the tube 
manufacturers provided that the scratches are not too deep. 

Although not strictly speaking a picture-tube fault, it is worth 
noting that as picture tubes age any deficiency in E.H.T. voltage 
tends to produce results akin to that of a " soft " tube or failing 
emission, and before deciding that a tube has no further useful 
life it is advisable to check the E.H.T. 

In addition to such work, thero are now a number of firms who 
specialise in salvage work for the trade. This includes fitting 
new cathode assemblies after opening the tube; or alternatively 
re-activating the cathode followed by a re-vacuuming process by 
heating the getter " with an R.F. heater. 

Correct Usage of Cathode-ray Tubes 

A British Standards code of practice (('.P. 1005 : 1954) on the 
use of cathode-ray tubes makes the following recommendations, 
on how to secure optimum performance and life : 

Manufacturers' ratings should never be exceeded. 

Heater voltage should not vary more than 5 per cent from the 
rated value; low voltages are as much to bo avoided as high 
voltages. Series connection of heaters should be avoided (this 
does not apply to certain modern tubes specifically designed for 
such operation). 

Television tubes which arc designed to operate in a scries heater 
chain should have the heater current restricted to 2-5 por cent 
of the rated value. 

Before applying a potential between the heater and cathode 
<>fa tube, the manufacturer's tube specification should be studied. 
If no maximum voltage is given it is better to restrict this value 
to the minimum possible, [ueferably less than :*i volts. 

When the tube is mounted horizontally, the correct method is to 
support the tube near the bulb at its maximum diameter and also 
to clamp tho nock lightly near, but not actually on, the base. 
The fixing should bo resilient, and metal-to-glass clamps avoided. 

(Contiiiurd on page 227) 



228 



TELEVISION ENGINEERS' POCKET BOOK 



CATHODE-RAY TUBES 



229 




(J 
o 


<X> 






y 

< 


< * 
o 


«tJD — f— 


H|l^ 


1 


z 



u 


t- 




in 


< 






y 


o 


2 






i 




ce 
















x* 




t- 






trO. 




~z 






<S 










ace 













rtD 



*JQ 




u 




230 TELEVISION ENGINEERS' POCKET BOOK 

Table 14.1. — Picture-tube Data 



Type 



(in.) 



Gun, 



Healer 



Base 



yutex 



firimar 
0UA 
Our; 

C12A 
01 2B 
C12D 
C12E 

C12FM 



C14BM 


11 


C14KM 


14 


C11GM 


14 


C14JM 


14 


014LM 


14 


014PM 


11 


015B 


15 


(J17AA 


17 


017BM 


17 


rl7FM 


17 


0I7GM 


17 


017HM 


17 


C17JM 


17 


C17LM 


17 


ciri'.M 


17 


C17SM 


17 


C21AA 


•Jl 


CS1HM 


21 


OSXKM 


91 


021NM 


21 


cji-su 


21 


C21TM 


•Jl 


024 KU 


24 


Cathcdem • 




oia i 


12 


ill g 


14 


C14/3A 


14 


017/1 


17 


i'17-lA 


17 


C'l 7/4A 


17 


017/SA 


17 


017/6A 


17 


(T7/7A 


17 


C81/1A 


21 


■ :sii j i 


14 


Co**or 




AW45-S0 


17 


A\\"4$-88 


17 


CRMlll 


14 


CHJ1142 


14 


CIIM171 


17 


OKM172 


17 


MW31-74 


12 


m\v:;g-44 


14 


MW43-00 


17 



Triodc 
Trioiie 
Triode 
1'ricitlc 

I node 

Triode 

Tetrode 

Triode 

Tetrode 

Hexode 

liexodc 

Efaxods 

llexode 

Triode 

llcxmlft 

Triode 

Tetrode 

Hexode 

Tetrode 

Hexode 

Hexode 

Hexode 

llexode 

I I I'M nit- 
Tetrode 
Tentode 
Pentode 
Hexode 
Tetrode 
t'entuilf- 



Tetrode 
ll-\.j.tc 
Hexudp 
Tetrode 
Tetrode 
Tetrode 
Eexode 
Hexode 
Etexode 
Tetrode 

Trrrn.lt> 



Heptode 
llexode 

Tetrode 

Tetrode 

Tc.trnilt; 

Tetrode 
Tetrode 
Pentode 
Pentode 



20 

2-0 

2-0 

20 

6-3 

6-3 

6-3 
12-3 
12-6 

6-3 

11 -3 

6-3 ; 

2-0 

(i-3 

6-3 I 
12-B 
12-6 

6-3 

6-3 

6-3 

0-3 

fi-3 

B-3 

6-8 

>;-;, 

0-3 

12-6 

6-3 



6-3 
i;-:: 
*;■:; 
6-3 
6-3 
6-3 
6-3 
6-3 
6-3 
6-3 
6-3 



6-3 
r,.:; 
12-6 
12-6 
li'.fi 
12-6 
6-3 
6-3 
6-3 



1-4 
2-5 
H 

2-5 
2-5 
0-6 
0-3 

ih; 
0-3 
0-3 
0-6 
iKS 

Q.J 
2-5 

<!■;; 

o-e 

0-3 
0-3 

o-u 

0-6 
0-3 
0-3 
0-3 
0-3 
0-6 
0-3 

a-a 

0-3 
0-3 
0-3 



0-3 

11-3 
0-3 
0-3 
n-3 

ii-:; 
0-3 
0-6 
0-3 
i)-3 
0-3 



11-3 
ii-;: 
0-3 
0-3 
0-3 
0-3 
0-3 
n-:: 
0-3 



M0(3) 

K(4) 

MO(5) 

K(4) 

K{4) 

K(4) 

B12A(2) 

B12A(1) 

B12A(2) 

B12A(9) 

B12A(9) 

B12A(9) 

l'.l-JA(U) 

K(4) 

itsrrnii 

BlSAflJ 
BlSAfSJ 

B12A/8) 

B.12A(2) 

KIJACU 
lU-'AC.i) 

in-jAC.o 

B12A(9) 
llSIIHl} 
B12A(2) 
B12A<3) 
M2A(3) 
B12A(9) 
B12A(2) 
B12A(3) 



l.UA.Ji 
l:r.'\.:<j 
B12A(») 
BltA(2) 
B12A(2) 

bisaTs) 

B12A(9) 
i'.sll.lli 

nsircii) 

B12A(2) 
B12A{2) 



B12A(9) 
BSH(il) 
B12AI2) 
B13A/2) 

iir.'A(2> 

U12AC0 
B18A/S) 

B12A(3) 
B12A(3) 



Al. 

AJ. 

Al. 

Obsolete 

I.T., K.C. 

E.O., Al. 
; T.T., B.C., AJ. (70°) 
' E.S., I.T., B.C., Al. (70°) 

B.S., I.T., B.O.. Al. (70°) 

E.S., B.C. A I. (70 ) 

BJB., l.r., R.O., At. (7i/-> 

Al. 

BA, Al.. B.O. (110°) 

B.C., AJ. (70°) 

I.T., B.O., Al. (70°) 

E.S., I.T., B.C., AL (70°) 

T.T., B.C., Al. 

K.S., I.T., B.C.. Al. (70°) 

B.C., Al. (7(1°) 
■' E.S., B.C., I.T., Al. (70° j 
j E.3., B.C., Al. (90 c ) 

K.S..A1., E.G. fill) ) 
I I.T., E.G., Al. (70°) 

I.T., B.C., AJ. 

I.T., B.C., At. 

E.S., E.G., Al. (80°) 

I.T., B.C., Al. i!t' i i 

B.C., Al.iui i t 



I.T., 
B.6. 
B.8. 

I.T., 

l.r.. 

I.T. 
I.T. 

k.s. 
K.s. 
I.T. 
I.T. 



K.C. 

I.T., B.C. 
. I.T.. K.C. .11.(70') 
. K.< .(70°) 
, E.O., Al. (70°) 
. K.C. AL(90 i 
, E.G., E.S., Al. (DO') 
. K.C, Al. (110') 
. B.I .. Al. hidn 
, E.C.. A I. 
, B.C. (70 i 



E.S., I.T., AL. B.C. (SQ"l 

. K.C. 1 1 in j 
1,T.,.\I. (67 s ) 
I.T., Al. Wl i 
T.T., AL m 'I 
I.T.. AL, B.C. (69 ; ) 
I.T., E.G. (63°) 
T.T., K.C. (70°) 
I.T., Al., E.G. (70=) 



• Bor Cathodeon "Popular" tubes, the prefix "X" is lused in plaec of "0" 
otherwise detuils are identit-nl /or both -series. 



CATHODE-RAY TUBES 



231 









/(, ■!'■ r 






Type 

i 


Sue 
(in.) 


Gun 




Base 


Jfotef 


V. | A. 


Cosw (coutd.) 










J1W..S so 


21 




6-3 0-3 


B1SA<3) 


I.T.. \l.. K.cr.io , 


i ■..■■!-: - 


15 


Triode 


4 " 1-1 


4-clip (7) 
4-elip (7) 


I.T. (40°) 


75K 


10 


Triode 


6-3 0-55 ' 


I.T. (52°) 


S5K 


15 


Triodc 


6-3 0-55 


4-clip (7) 
4-clip (7) 


i:r. (52°) 


1Q8K 


10 


Triode 


6-3 0-55 . 


T.T. (50°> 


112K 


l-J 


Tetrode 


6-3 0-3 


BMA/S) 


Obsolete 


121K 


1^ 


Tetrode 


6-3 0-3 


tU-JA(2) 


Obaol. I.T., B.C. (00°) 


141K 


II 


Tetrode 


6-3 0-3 


1U2A(2) 


Obsot. I.T., E.G. (70°) 


171K 


17 


Tetrode 


6-3 0*8 


B12A(2) 


Obsol. I.T., E.G. (70°) 


172K 


17 


Pentode 


6-3 0-3 


i:UAt:;i 


Oh-ol. I.T., E.G. (70 8 ) 


173K 


17 


Pentode 


6-3 0-3 


lU'JAC'.) 


Ol.-ol. I.T., K.C. A l.(7'i . 


212K 


21 


Pentode 


6-3 


0-3 


lU'JA(:i) 


T.T., E.G., Al. (90°j 


Edit wan Mazda 












CMR141 


1-1 


llexode 


12-6 


0-3 


I'.IJAC.i) 


E.S., E.G., AL, T.T. (70°) 


CM B MO i 


11 


Hexode 


12-6 


0-3 


i:t-JA(LH 


B.S., B.C., AL, I.T. (90°) 


CME170S 


17 


Hexode 


12-6 


0-3 


BlSArt) 


K.S.. K.C, A1.(B0") 


CME1708 


17 


Hexode 


12-6 


ii-:'. 


j:>llill) 


K.S., Al.. K.C. illu) 


CME1705 


1" 


Pentode 


12-6 0-8 


B8n 


B.S., Al., E.G. (1 1" i 


CMB«01 


21 


Hcxndc 


u-e o-3 


B8BX1I) 


K.S.. Al„ B.C. (110 


i liM'.U 


U 


Triode 


20 1 1-4 


MO(S) 


(04°) 


CKM',12 


9 


Triode 


2-0 1-4 


MO(5) 


(675 


CHM92A 


y 


Triode 


2-0 1-4 


MO(5) 


(57°) 


CliM'.i:! 


9 


Tetrode 


12-6 0-3 


Iil-JA(Jl 


I.T., Al. 


C11M121 


12 


Triode 


2-0 1 1-4 


MO(5) 


(57 s ) 


CKMI2IA 


12 


Triode 


20 1 1-4 


MO(5) 


(57°) 


OBM121B 


12 


Triode 


2-0 | 1-4 


MO® 


(57°) 


CUM 122 


12 


Triode 


7-3 


0-3 


MO(5) 


(57°) 


GUM123 


12 


Triode 


20 


1-4 


MUf-Ji 


AL (57°) 


i-BMIS-l 


12 


Tetrode 


12-B 


0-3 


B12AC2) 


I.T., B.C., Al. (57°) 


riiMlll 


14 


Tetrode 


12-6 


0-3 


U12A(2) 


T.T., Al. (67°) 


0RM149 


11 


Tetrode 


U-fi 


0-3 


IJ12A(2) 


I.T., A 1.(67°) 


CBM143 


1 1 


Tetrode 


12-6 0-3 


HI2A(2> 


I.T., Al. (70°) 


( -11M144 


11 


Tetrode 


I2-C D". 


B12A(2) 


I.T., E.C., AL (70°) 


i KM 151 


15 


Triode 


2-0 1-4 


MO(5) 


AL (51°) 


CUM 162 A 


15 


Triode 


20 1-4 


lU-JA(l) 


A 1,(67") 


CKM152B 


13 


Triode 


2-0 | 1-4 


B12A{1» 


Al. (67°) 


CRM153 


15 


Tetrode 


12-6 I 0-3 


B18AP) 


I.T., Al. (67°) 


CRM171 


17 


Tetrode 


12(1 i»-3 


H12AC2) 


I.T., Al.il'.H i 


GUM 172 


17 


Tetrode 


12-6 ! 0-3 


I'.i-jacJ) 


J.T., E.O., AL (69°) 


i'i:M173 


17 


IVU-|>.|.! 


12-fi D-3 


B12A(2) 


T.T., B.C., Al. (90 -) 


<i:M-.'lt 


21 


Tetrode 


12-li "1-3 


nuArji 


I.T., E.G., Al. (7iP) 


( i;M212 


21 


Tetrode 


12-6 0-3 


Hl-JAfJl 


I.T., B.C., ALU" ii 


CKM241 


24 


Tel rod.: 


12-fi H-3 


1!12A(2) 


i.l.. !■;.( '.. Al. (90°) 


J4W6S-30 


21 


Tentode 


6-3 i 0-3 


B12A(3) 


I.T., E.C., Al. (70° 


KmUeope 












3 1 


5 


Triode 


, 4-0 1-3 


Side -wire 


01>solete 


:. -j 


7 


Triode 


4-0 1-3 


Side-wire 


(Jlisuli-li- 


3,'3 


9 


Triode 


! 4-0 1 1-3 


Side-wire 


Obsolete 


:; \ 


10 


Triodc 


4-0 1-3 


;-i-!i -\vi;-t- 


Obsolete 


3/5 


14 


Triode 


in 1-3 


Si de-wire 


Obsolete 


3/6A 


13 


Triode 


4-<i 1-3 


.Side- wire 


Ofaeotote 


:; in 


10 


Triode 


| 13-3« 0-3 


7-pin (2) 


AL 


3'18 


12 


Triode 


13-3« 0-3 


7-pin (2) 


, Al. 


3/20 


ID 


Triode 


11-5 0-3 


4-elip (7) 


1 Obsolete, I.T. 



• Has been progresstrely reduced to 8-6 volts at 0-3 amp. 



232 



TELEVISION ENGINEERS' POCKET BOOK 



Type 



Siu 
(in.) 



Bmiscopc (contd.) 



:; :;i 


1 '- 


3/32 


15 


4/13 


1 21 


4/I4T 


14 


4/14TG 


Jl 


4/1 6T 


17 


4/15TG 


17 


5/2 


14 


5/2T 


14 


r, ;: 


1 17 


5/3T 


17 


G/5 


1 9 


6/6 


[ 12 


SKI 4/70 


If 


SE17/70 


17 


TA10 


10 


TA15 


15 


EmitTon 




12X1 '4 


12 


12XIMA 


12 


14JCP4 


14 


I4KPIA 


14 


14LP4 


14 


im:i'-i 


15 


17ASP4 


17 


17AXP4 


17 


s,",K 


15 


108K 


10 


English Elect 


ric 


T901 


16 


'I'HOIA 


16 


T90i 


11 


T1KJ6 


14 


Tims 


17 


Till lit 


21 


Tuiwa 


21 


TB11 


17 


T914A 


17 


T915 


21 


Ftrranti 




T9/2 


9 


Tii :>. 


9 


T9/5 


9 


T12/2 


12 


'IT 2/44 


12 


T12/46 


12 


TI2 54 


12 


T 12/56 


12 


T12/71U 


12 


T12/72U , 


12 


TI2/8IU 


12 


T12/82U 


12 


T12/9J 


12 



Ova 



Triode 

Triode 

Tetrode 

Tetrode 

Tetrode 

Tetrode 

Tetrode 

Pentode 

Pentode 

Pentode 

Pentode 

TTexodo 

Eexode 

Hexode 

11 ex ode 

Tetrode 

Tetrode 



Tetrode 
Tetrode 
Tel rode 
Tetrode 

Tetrode 

Tetrode 

Tetrode 

'IVm.de 

Triode 

IV i ode 



Tetrode 
Tetrode 

T.-Ir,,,d»- 
I ; trn !:■ 

Tetrode 
Tetrode 

Tetrode 



Triode 
Triode 
Triode 

Triode 
Triode 
Triode 
Triode 
Triode 
Triode 
Triode 
Triode 
Triode 
Triode 



Heater 



13-D* 0-3 
13-0*1 0-3 

13-oH 
l.VO 
13-0«" 
13-0»| 



n. 3 
0-3 
0-3 
0-3 



13-0» 0-3 



<;■:: 
6-3 
6-3 
6-3 
6-3 
G'3 



6-3 
6-3 

fi-3 
6-3 
6-3 



0-3 

0-3 

0'3 

0-3 

0-55 

ii-,V. 



...f, 
0-3 

0-3 

0-3 



6-3 


0-3 


6-3 


0-3 


6-3 


0-3 


6-3 


0-3 


4-0 


10 


4-0 


1-0 


40 


10 


■Ml 


1-0 


4-11 


95 


6'3 


0-6 


-|.f) 


0-95 


6-3 


0-6 


8-0 


0-3 


80 


0-3 


K-0 


0-3 


8-0 1 


0-3 


2-0 


1-5 



Base 



, 8-5 


0-3 


8-5 


0-3 


' 8-5 


0-3 


8-5 


0-3 


4-0 


1-3 


4-0 


1-3 


6-3 


0-3 


6-3 


0-3 


4-0 


10 


40 


1-0 


6-3 


0-3 


6-3 


0-3 


6-3 


0-3 


6-3 1 


0-3 



B12A(2) 
B12A(2) 
B12A(2) 
K12A{2) 
B12A(2) 
BI2A(2) 
J)I2A(2) 
HI2A(2) 
4-c!ip (7) 
4-clip (7) 



B12A(2) 

BI2A(2) 

BUJAfSl 

B12A(2) 

B12A(2) 

B12A(2) 

BIL'A 

H12A(2) 

B12A 

U12A 



KM) 

KM) 
K(4.i 
K(4) 
K(4) 
K(4) 
K(4) 
K(4) 
K(4) 
K(4) 
K{4) 
J£(4) 
K(4> 



A'otes 



CATHODE-RAY TUBES 



233 



7-pin (2) 
7-iiin (2) 
7-pin (3) 
7-pin (3) 
7-pin (1) 
7-pin (3) 
7-pin (1) 
7-pin <3) 
7-pin (3) 
7-pin (3) 
7-pin (3) 
7-pin split 
7-pin split 
B12A 
B12A 
7-pin (1) 
7-pin (1) 



AJ. 

A I. 

Obsolete, AJ. 

A!. 

AL, E.C 

Al. 

Al., K.C. 

K.S., Al. 

K.S.. A I, 

!■:..-,. Al., E.C 

BA, Al., E.C 

E.S. 

IX, Al., E.C. 
I.T., AJ., B.C. 
Al. 

Al. 



E.G. 



ObsoL I.T., E.C. (60°) 
I.T., E.C. 
OtaoL I.T., E.C. 
Obeol. I.T., K.c. (70°) 
I.T., E.C. (70°) 
I.T., E.C. (52°) 
Obrfol. I.T., E.C. 
I.T., E.C. (70°) 
ObsoL l.T. (52°) 
ObsoL l.T. (50 8 > 






I.T., Metal cone 
l.T,. Metal cone (70") 
Obsolete, I.T., B.C. 
Obsolete, l.T., E.C, 

l.T., K.C 

Metal cone 

Metal cone 

K.C, Al. 

Al. 

AL, Metal cone 



M. 



l.T 
l.T, 

l.T. 
l.T 
l.T, 



Obsolete 
Obsolete 
E.C. 
Obsolete 

Obsolete 
Obsolete, E.C. 

Obsolete. l-;,( . 

Obsolete, E.C. 
E.C. 

Obsolete, Al. 
Obsolete, B.C., Al. 

Obsoleh- 



Type 



Size 
(in.) 



Ferranti (contd.) 
'IT 2/92 I 1 
IT 2/100 
TI 2/404 
Tl 2/449 
TI2 504 
T12/D49 
TR14.1 
TK14/2 
TR14/4 
TR14/8 
TKM.-12 
TKJ4.13 
TR14 IS 
I'll 1 1 21 
TRI4/22 
TK17 I 

Tin: 2 

TBI 7/7 
TR17/8 
TBI 7/10 
TB17/21 

TBI 7/22 
TB21/21 
TR-'I 22 
MW31-74 
MW 36-24 
MW 36-14 
MW43-64 
MW-13-69 
MW53-80 



O.E.C. 
6502 
6503 
6504 
6504A 
6505 
6505A 
6B06A 
6703A 
6704A 
6705A 
6706A 
UNOtA 
•o"2A 
6901A 
7101A 
7102A 
7201 A 
7203A 
7204 \ 
7205A 
7401 A 
7404A 
7-H 15 A 
7406A 
7501A 



* Has been progressively reduced to 8-6 volte at 0-3 amp. 



Gun. 



Triode 

Tetrode 

Triode 

Triode 

Triode 

Triode 

lit ode 

JYiode 

Triode 

Triode 

Tetrode 

1 etrod ■ 

Tetrode 

Tetrode 

Tetrode 

Trio.ii-- 

Triode 

Tetrode 

Tetrode 

Tetrode 

Tetrode 

Tetrode 

Tetrode 

Tetrode 

Tetrode 

Tetrode 

1'cntodc 

Pentode 

Pentode 

Pentode 



Triode 

Triode 

Triode 

Triode 

Triode 

Triode 

'IViode 

Triode 

Triode 

Triode 

Triode 

Triode 

Triode 

Triode 

Triode 

Triode 

Triode 

Triode 

Tetrode 

llexode 

Triode 

Tetrode 

TTexodc 

1'entode 

Triode 



Heater 



2-0 
6-3 

4-0 
4-0 
4-0 
4-0 
4-0 
4-0 
6<3 

e^s 

6-3 
,;■;; 
6-3 
6-3 
6-3 
4-0 
lii 
fi-3 
6-3 
6-3 
6-3 
6-3 
6-3 
6-3 
C-3 
6-3 
6-3 
6-3 
<;-:; 



10-5 
6-3 
6-3 
I i.i ■ ■:, 
10-5 



Bast 



1-5 

0-3 

0*8* 

0-95 

0-95 

0'95 

0-9S 

IHly 

0-3 

0-3 

0'3 

0-3 

0*8 

0-8 

0-8 

0-95 

0-95 

0-3 

0-3 

0-3 

D-S 

0-3 

0-3 

0-3 

d-:i 

0-3 

0-3 

0-3 

n-.'i 

0'3 



0-3 
0*8 

0-5 
0-5 
0-3 
0-3 



6-3 I--:: 
ti-:; ic5 



10-8 

«■:: 
10-5 
6'3 
6-3 
6-3 
6'3 
6-3 
<;■:; 
6-3 
12-6 
J 2- 6 
6-3 
12-6 
12-6 
12-6 
6-3 



0-3 
0-5 
0-3 
0-5 
0-3 
0-3 
0-3 
0-3 
0-3 
0-3 
0-3 
0-3 
0-3 
0-3 
0-3 
0-3 
0-3 



K(4) 

]tl2.\l'2l 

K(4) 

B(4) 

K(4) 

K(4) 

K(4) 

B(4) 

K(4) 

B12A(1) 

R12A(2) 

BISA/Sj 

B12A(2) 

B12A(2) 

B12A(2) 

K{4) 

K(4j 

i;i2A(2) 

B12A(2) 

HI2A(2) 

B12A(2) 

B12A/2) 

BlSACa) 

B12Af2) 

B12A(2) 

BISAft) 

B12A(3) 

B12A(3) 

B12A(3) 

B12A(3) 



' K<4) 
K(4) 
K(4) 

K(-l) 

KM 

K(4) 

K(4) 

KM) 

KC4) 

K(4) 
I K(4) 
I K(4) 
' K(4) 

IU2A(1) 

K(4) 

B(4) 

B19A<1) 

B12AC1) 

B12A(2) 

BlSAfSl 

B12A(1) 

B12A(2) 

BSU(ll) 

B8H 

B12A(1) 



Nates 



B.C. 

I.T., K.C. 

Obsolete, 

Olwolete 

Obiulete, 

E.C. 

Obsolete, 

I l',~n:n:->. 

Obsolete, 
B.C.. A I. 
Obsolete, 
Obsolete, 
Obsolete, 
I.T., E.C. 
I.T., K.C. 
Obsolete, 
Obsolete, 

i Obsolete, 
Olwolete, 
Obsolete, 
Obsolete, 
l.T.. K.C. 
Obsolete, 
Obsolete. 

! l.T., B.C. 
I.T., E.G. 
I.T., K.C. 
Obsolete, 

I l.T., AL, 

| I.T., Al., 



Al. 

AL, E.O. 

Al. 

E.C, Al. 
E.C, Al. 

AL 

E.G., Al. 
K.O, Al. 

, Al. 

Al. 

E.C., Al. 

Al. 

E.C, AL 

E.G., Al. 

I.T., E.C 

, AJ. 

I.T., E.C 

l.T,, E.C, AL 



T.T., E.C. 

K.C 
E.C (90°) 



Obsolete 

Obsolete 

Obsolete 

E.C, AL 

Obsolete, E.C. 

E.C, Al. 

Al. 

Obsolete, E.C, AL 

Obsolete, E.C, Al. 

Obsolete, E.C, Al. 

Obsolete, E.C, AL 

A I. 

Al. 

A I. (70=) 

K.C., Al. 

E.C, AL 

K.C., Al. 

E.G., AJ. 

E.C, Al. 

B.S., l.T., E.C, AL 

E.G., Al. 

K.C. Al. 

E.S., AL, E.C. (110°) 

E.S., AL, E.C (110°) 

E.C, AL 



234 



TELEVISION ENGINEERS' POCKET BOOK 



CATHODE-RAY TUBES 



235 









Unit- r 






Type 


Site 


Oun 






Rase 




V. 


.1. 


.V"'- | 


Q.E.C. (eorittl.) 












raosi 


21 


Tetrode 


12-6 


0-3 


B12AC2) 


E.G., Al. 


760SA 


21 


Hexode 


12-6 


0-3 


HMIillj 


&S., Al., F.r. iiin i 


J/ittfarrf 














MW'fi 8 


21 


Triode 


6-3 


0-3 


S.C.(8) 


Projection tube, E.G., Al. 


MW22-7 


8 


Tetrode 


6-3 


0-6 


i'.xiir.i 

l!-.(|-,| 


Obsolete 


MW22-U 


•J 


Tetrode 


8-3 


0-3 


Obsolete 


MW22-1 If 


a 


Tetrode 


C-3 


0-3 


H8G(S) 


Obsolete 


MW22-1G 


9 


Tetrode 


6-3 


0-3 


itii'Aiaj 


I.T., E.G. (60°) 


MW22-17 


9 


Tetrode 


6-3 


0-3 


H12A(2J 


Obsolete 


Mwaa is 


B 


Tetrode 


6-3 


u-.-i 


B13A(3) 


Obsolete, E.G. 


H (781.-7 


12 


Tetrode 


6-3 


....; 


B8G(8) 


Obsolete 


MW81 M 


12 


Tetrode 


6-3 


0-3 


B8G(6) 


Obsolete, E.G. 


MW81-140 


12 


Tetrode 


6-3 


0-3 


j:x; ( ii, 


Obsolete 


MW3I-I6 


12 


Tetrode 


6-3 


0-3 


I!I2.\(2) 


Obsolete, IT., E.G. 


MW31-17 


12 


Tetrode 


6-3 


0-3 


B12A(2) 
R12A(2) 


Obsolete 


MW31-1S 


12 


Tetrode 


6-3 


0-3 


Obsolete, B.O. 


AUV31-2U 


12 


Tetrode 


6-3 


d-3 


BSG(6) 


Obsolete 


MW31-21 


12 


Tetrode 


6-3 


0-3 


B8QC6) 


Obsolete, B.C. 


MVV31-22 


12 


Tetrode 


B-n 


0-3 


lIPJACij 


Obsolete 


MW31-23 


12 


Tetrode 


6-3 


0-8 


B13A(8) 


Obsolete, B.C. 


MW31-71 


12 


Tetrode 


ii-;; 


0-3 


BlSAffl 


T.T., E.G. (80°) 


MW36 22 


14 


Tm r< ii lc 


6-3 


0-3 


BI2A(2) 


Obsolete, I.T., E.G. 


MW 36-24 


14 


Tetrode 


6-3 


0-3 


R12A(2) 


I.T., 0,0. (70°) 


MW 36-14 


H 


Pentode 


6-3 


0-3 


B12A(3) 


I.T., B.O. (70°) 


MW41-1 


18 


Tetrode 


6-3 


ii-:; 


B1SA(2) 


I.T., Met. (70°) 


KW48 18 


17 


Pentode 


6-3 


0-3 


B12A(3) 


I.T., Met. (70°) 


M W43 -64 


17 


Pentode 


6-3 


0-3 


1U2A(3) 


I.T., E.G. (70°) 


\nvi:; .;■! 


17 


Pentode 


6-3 


0-3 


H12A(3) 


T.T..A1., H.C. (70') 


M W43-S0 


17 


Pentode 


B-3 


0-3 


B12A(3) 


I.T., AL, E.G. (90°) 


MW53-20 


-.'1 


Pentode 


6-3 


(1-3 


HI2A(3) 


I.T., Al., E.G. (70°) 


MW53-80 


21 


Pentode 


(i-3 


0-3 


B12A(3) 


I.T.. Al., E.G. (00°) 


AW36-20 


14 


lieptode 


6-8 


0-3 


B1»A<9) 


I.T., .E.C, BA, Al. (70°) 


AW 3(5-21 


14 


Heptode 


8-3 


0-3 


B12A(9) 


E.S., T.T., E.C. (70°) 


a w 88-80 


II 


Heptode 


6-3 


0-3 


M2A{9; 


I.T., E.G., E.S., Al. (90°) 


AW43-S0 


17 


Heptode 


(;■;> 


0-3 


H12A('J> 


E.3., J.T., E.C. (90°) 


AW. (3-88 


17 


M CM l> If 


6-3 


0-3 


B8H{11) 


BA,Ai, E.C. inn i 


AW53-80 


21 


Heptode 


fi-3 


0-3 


B1SA(9) 


E.S., T.T., E.G. (90°) 


LWS8-8S 


21 


Hexode 


6-3 


0-3 


lisiiai.i 


E.S., Al., E.G. (110' ; ) 


i J ('nnae/e 














P12 


12 


Tetrode 


6-3 


0-3 


B12A(2) 


I.T., E.C. 


P14 


11 


Triode 


6-3 


0-8 


B12A(1) 


I.T., E.G. (Obsolete) 


P14BS 


14 


Heptode 


8-3 


0-8 


B13A/9) 

B12A(3> 


K.S., 1.1'., E.C (70') 


Pi7 


17 


Tetrode 


6-3 


0-3 


I.T., E.G. 


P17A 


17 


— 


6-3 


0-3 


BT8A(3)or BJ 


I.T., AL, E.C. 


PL 7AM 


17 


I ■! ri iic 


12-6 


0-3 


B12A(2) 


I.T., Al.. LLC ifiy , 


P17HH 


17 . 


fli'Miilr 


6-3 


0-3 


liSHUlt 


E.g., AL. H.C. ill' i J 


! ■ 1 7KN 


17 


Heptode 


6-3 


i.'-3 


B18A(8) 


K.S.. i !■;.' , w . 


PI7M 


17 


Tetrode 


6-3 


0-3 


B18A(Sl 


I.T., E.C. (70°) 


P17MN' 


17 


IV- tmlc 


6-3 


0-3 


B12A(3> 


LT„ AL. B.C. (90 ) 


ri4i 


14 


Tetrode 


6-3 


0-3 


lil2A(2) 


I.T., E.O. 



Table 14.2. — Cathode-rav-ti:bk Kqiivalkms 



A'otw.— E.S. = electrostatic focusing; E.G. — external conductive coating; I.T. = 
ion trap fitted; AL ■= alumiuised screen; Met = metal cone. Begrees in brackets 
are deflection angles. Xmnbers in brackets alter base tvpe refer to diagrams on 
pages 226 and 227. 



TW 



/■:>/!/ irahnts ° 



LWS8 81 

\wr, 30 

auk 58 
AW53-8U 
\\\:,:\ 88 
CM 

C18A 

CUB 

C18D 

CISFM 



C 1 1 ;;.\ 

014PM 

CI. -' It 
C17-1A 
017 2 

< i;aa 

' -JlAA 

' '21 KM 

C31TM 

CMB1402 

OMB1708 

CMB170S 

OMBS101 

CBM71 

C If Mil I 

CEM88, a 
0B.M181, 

A. B 
CBM1 II 
CKM172 
CHM212 
MW8 a 
MW18 2 
MW89 :: 
MW31-16 

MW31-18 
MW31-74 

MW36-21 

MU41 1 
MW43-61 



P14BS 

P17NN, 17HTP4, i74K, 

I '17 r.A 
i'17\A, P17BH, CI 7 7A 
•JU'Ll'l 
08UU 

■ f:\H»2 % CRM92A 
CRM121. CBM121A, 

OBJOSIB 
12M\v::a 
L2MW3 
121 K, 12XP1. KW81-18, 

M\\:n-74, Pt2, TI-' I'm, 

018 1 
1 1] 4PM.SB14 7n 
I'll 3A.SB14 7" 
LBMWSi 

MM i:; B9.TB17 S3 
1CW4S-89 
A W 1 3-88 
AW53-88 
M\\ 83-80 
MW88 21 
7809 \ 
7406A 
741 Hi A 
7803A 
HW18 3 
MW22 :>. 1 18 v 
MW'22 3. 08A 
C12A. ( I'.MC.'l 

72KI.V 
71"IA 

7S08A 

;i.M'-v 

0BM71 

CltM92 

013PM, 121 K. 12X1M, 

MW81-74, CIS l 

IIJK 

CI2FM, 121K, 12XP4A, 

CI 2 I 
ItIK, MKI'I\. 111.1'!. 

<■;;« 2i 
T'.nil. TSXIl.V 
172K, MVV43-6B, C17 1, 

TBI" 21 



Tip* 



Entih-uliiitx 



SlWiZ-m C17 8, 172K, 173E, P17A. 

TB17/88 
MW6S-80 C21KA1, C21 1A, 212K. 

TR21 89 
MW6S 88 C2IKM 
P12 MW31 16. MW31 71. T12/ 

100, 0T2BM, J2X1>1A, 

121K 

P14 G14BM, TH14/13. 7201 A 

P14B8 AW3B-21 

B17 MVV13 (U.TU17 21.17A~I'L 

17^1v 
P17A MAVi:; 88, C17-1A. 172K, 

173K 
P17AM CUM 172, 7 I" I A 
PI7KH AW43-88, C17AA 
P17BK AW 13 Si). 171E. 
P17MK MW43 80 
P141 1 UK. IIKL'1. IlKl'll 

HK117U C14PM 1 C14'3A 
SK17 7" C17PM 
T12/2 C18D 

T12 \tw:;i ri 

T'JOl. A il\V41 1 

18MW8 01 2B, T12/48 

12MW3A i:i2M 

18XP4 018TM,MW81 16.MW31-71 

12XP4A MW31-74, 121K.C12 I 

HKI'IA 1HK. MW88 34. ' "U-2-t 

1.1MW3A C1SU 

17A8P4 171K,C17 1 

17AX1M 1 71 K (near) 

112K MU'31-18, CI2FM. I2XT4 

121E MW31-7S, otc. 

I UK MVV3B-24, P141, 11KP1A, 

038-24 
171 K 17ASP4, C17 1 

I72K MW13-6-1, MWt;: Ii'.'. (17 2, 

PIT A 
17SK MW43 (ill. CI 7 2, PI 7 A 

212K MW.73-8«J,C21 IA 

7804A ili.MIll 

7303A IMF, 14"-' 

740-1A ('KM I 72 

7 10r, A CM El 7(13 

74048 CMB1705 

rSOSA OBM813 

7503A OMB2101 



• Xote: Not all types shown are direct equivalents but should prove satisfactory 
n: placements. 



236 TELEVISION ENGINEERS* POCKET BOOK 



Table 14.3. — Picture-tube Replacement Table 



Original 
Tube 



Replacement 



Modifications 



Cossor 




SB K 


I 80K/2 


112K 


MU:;i-74 


121K 


KW81-74 


14IK 


MVV36-44 


171K 


MV. 43-69 


178K 


MW43 63 


173K 


MW43-68 


Emiicape 




3/3 


TA10 


3/4 


IA10/J 


3/5 


TA 1 5 .1 


:; fiA 


TA ! r, .1 


3/20 


3/16 


5/2T 


.-KM; 7" 


5/3T 


SB17/70 


Ferranti 




T9/2 


T9/3 


T12/2 


1 !!■ .11 


T12/46 


T12/44 


T12/54 


T12 .VIII 


til> r.e 


Tl- .VI U 


T12/71IJ 


T12/72U 


T12/SM 


T12/72U 


T12/82U 


Tl'J :- ! : 


Tl 2/404 


T12/44 


T1 2/449 


112 II 


IT.' fxM 


Tli .VI U 


TR14/2 


TK14/8 


Till 4, '4 


TR14/8 


TR14/15 


TRI4/I3 


TBI 7/2 


TR17/21 


TR17/8 


TK 17/10 


G.E.C, 




6703A 


7101A 


6704A 


7101A 


G705A 


7102A 


8706A 


7102A 


ifatda 




URM91 


CRM91, 92, 92A 


OBM93 


CRM92, 92A 


CRA1I21 


CRM121, 121A. mi! 


CRM121A 


C11M121A, 121 B 


CKM121B 


CRMI2IB, C11M123 


CRM152A 


CRM152A, 152B 



Fir inn trap 
Pit inn trap 

Ensure that any connections to pin 7 arc 
rammed and anchored elsewhere. Then 
connect pin 7 to pin 11 

See nolo on 141K 



Modification 
Mml ideation 
Modification 
Modification 
Mortification 
Mortification 
Modification 



kit AK3M 
kit AK321 

kit .vi-::; i:: 
kit AE313 
kit AK3I2 
kit AK3S6 
kit AE386 



i Change mask Tl 2/44 has a flat face 
Insert 2-o-ohm, 2-5- w. resistor in series with 
one heater lead 

Insert 2-5-ohm, 2'5-w. resistor in series with 

one heater lead 
Earth external conductive coating 
Earth asternal conductive coating 



Refer to manufacturers tor modification' da I ;» 
Change valveholder to duodecal type 

Refer to manufacturers for modification data 



►•Note differences I n heater ratings 



Physical dimensions of CBM92 and CRH92B 
differ from CRM9I 



CRM123 provided that the E.H.T. exceeds 

7-5 kV. 
CRM152B has a grey face 



CATHODE-RAY TUBES 



237 



Original 
Tube 



Replacetnent 



Mollifications 



Mnllard 
HW32 r 



MW22-16 



MTT22-14 MWffl 18 
MW22-11U MW22-16 

MW22-17 ; MW22-16 
MW22-18 I MW23-I6 
MW31-7 MW31-74 

MW31-14 | MW31-74 
MW31-140 MW31-74 



MU'31-16 
MWS1-17 
MW31-J8 
IfCTftl-Hj 

MW31-2I 
MW31-22 

MW»1 23 
MW 36-22 
KW43 64 

I 'Itflltlllllll 

117 2 
CIT'BA 



MTV31-74 
itWtt-74 
MW 31-74 

m\v;;i 7i 

MW 31-74 
MTV' 31-74 

MW31-74 
MW 36-14 
MW43-69 



CI 7 1 orX17 1 

C17,7AorX17 



Pit ion-trap 
niajmet type 
IT6 a 



Change base, earth external' 

coating 
Change base 
Change base, earth external 

coating 
Earth external coating 

Change base, earth external 

coating 
< IbangG base 
Change base, earth external 

coating 

Earth external coating 



Change base, earth external 

coating 
Change base 
Change base, earth asternal 

coating 
Change base 
Connect pin 7 (a2) to pin 11' fk) 



Remove 0-6 amp. heater transformer, insert 
tube heater in series heater chain. 



Fit ion-trap 
magna! 

ito* 



* This may necessitate modifying the rear tube support, and in some receivers 
this modification cannot he made- In such cases further instruct inns regarding 
replacements can he obtained from Technical Service Dept., Milliard Ltd. 

The connections to the socket should also bo flexible, 1'rovision 
should be made for the rotation of the Kobe. 

There should be adequate ventilation to ensure a safe touipera- 
ture under all conditions, and it should bo appreciated thai the 
heat generated in adjacent components may largely determine 
the final temperature of the tube. 

The potential difference between the heater and cathode should 
not exceed SO V. except where this* in specified by the manuhiei iirer. 

There must always be a D.C. connection between each electrode 
and the cathode. The resistance of this connection should be 
: he. minimum pracl tea bio. 

Care should be taken to avoid scratching or otherwise damaging 
the surface of the glass. 

To ensure maximum cathode life, tubes should be run at the 
minimum useful brightness. 

To prevent damage to the screen material, tubes should not bo 
operated with a stationary or slowly moving spot, except at low 
beam current density . 

Stray magnetic fields may produce serious, advorse effects. 
Interference from such fields may be minimised by the suitable 
spacing and orientation of neighbouring components. 



[SECTION 15] 

VALVE DATA 

This section gives heater ratings, valve-base connections and 
equivalents for the valves commonly fitted to modern television 
receivers. 

Symbols Used to Indicate Fin Connections 

The recommended electrode letter symbols of the British 
Standards Institution, listed in B.S, 1409 : 1947, have, wherever 
possible, been followed. Those used in the tables on the follow- 
ing pages are explained below 



a 
k 

g 

h 
f 

M 



external conduc 



anode 

cathode 

grid 

heater 

filament 
tive coating 



internal shield 



In eases where a valve has more than one electrode system 
of the same type, eleetrodos of the same type are distinguished 
by the addition of " primes ", The example below is for a double 
diode with separate cathodes : 

k' a" h h k" s a' 
En the case of multiple valves using different electrode systems 
the respective electrodes are distinguished by the addition of the 

following subscripts : 

d ....... diode 

t ....... triode 

P •■..... pentode 

h . . . . . . hexode, hoptode, etc. 

For example, in the case of a double-diode triodo with common 
cathode, the following symbols would be used : 

g k h h a' d a" d a^ 

Subscripts are omitted wherever confusion is not likely to arise, 
for example in the case of the grids in the pentode system of a 
triode pentode. 

Valve Practice 

The following are among the recommendations made by the 
British Valve Association for the correct use of valves : 

Manufacturers' ratings should be carefully observed. 
23S 



VALVE DATA 



239 



Heater or filament voltages should not vary by more than 7 
per cent from rated values. 

The potential difference between the cathode and heater 
should not normally exceed 150 V unless the valve has been 
specially designed for A.C./D.C. operation. 

Ventilation should be adequate to ensure a safe bulb tempera- 
ture at all times. 

A limiting resistor should always be placed in series with a 
rectifying valve when used in conjunction with a condenser- 
input filter. 

It is generally undesirable to use spare socket contacts as 
connecting tags. 

There should always be a D.C. continuity between each 
electrode and cathode; and the resistance of this connection 
should be the least practicable. 

The heat dissipated at the electrodes should be the minimum 
possible : common causes of excessive dissipation are incorrect 
tuning of associated circuits, unnecessarily high no-signal 
currents, or parasitic oscillations. 




BRITISH 


BRITISH 


BRITISH 


SIDE 


U.X.4PIN 


4 PIN 


5 PIN 


7 PIN 


CONTACT 




(A Base) 


(0 Base) 


(M Base) 


(P Base) 






7 PIN 8 PIN L0CTAL 

MINATURE MINATURE (B8G) 

(B7G> (BSA) 



OCTAL 
(K Base) 



B3G 



SPECIAL 1 SPECIAL 2 




240 



TELEVISION ENGINEERS' POCKET BOOK 



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VALVE DATA 



241 



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a. -5-a oS* g g g 9,o g a g *>§""" 

"S ~~"3"i^,i.i - -fli .JLo >&§•<?■ 

.2 .2 .E .=: .= e b i s- - ar ^ Pa =; s & -e t5 15 

£ h £h=- > > = - = > e: > ^.c ooc 



~X7 



>i a "tis--^ £> 



242 TELEVISION ENGINEERS' POCKET BOOK 









iaasa **\ lil ii 1*1 i i ii is ^ iSS | | | 



A.d -a a a 1a4 « ** - I I \\ 






« Zxxm I Ue.*- I | ZJgj s I I s-a jmj 



tj ii — ^ • « 



*£££« !-^-i : =^-^ai * - s -^ {•**$***,,,, 



&i.li:i ,«*«! 



I i 1 Is. 



ti ^ a 3 a tx at. 



1*1 



?£ = ^ ; r?9?> = »9 9™« «» = ««=,§„-. « =t cr p, « 3 - « 






ill 



~jh- lAa 






'— S3 \_ 
fill 



1 2 M ■- I! ^ .£ 



1 « o » e « ■- 






&?? f f £?'! 









nRmn)5n 



3 1 


— 


© © © 

— — ■a 


Sa 


e 




fe§ 








- 1 S 

— - — 














^r 






-- 


^r 


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QBd 


HW 


5 


ooo 



i c -o = £.£.5.2 
£.— £i. = S. 3 & a c. a. 

K .2 .a .£ e; ■£ T3" *£ "ti 






--. 



T 

I 

I 




VALVE DATA 



243 



1 I 


, r - -. r. -, r. .-. 7' *. r. -,._..... 


nn 


9 


« 


-J 

- 


■4 

- 


7. r. 

sq 


I 

I 

K 


i 


] ! a | - 1 1 a * 1 1 !»tt»l 1 1 


1 1 


1 


1 


1 


1 


1 1 


39 


i 1 tS 1 i i &£&&£ei! 1 1 1 1 ="c x n 


"a Bfi 


6 




8 


-7-,' 


00 


j=js £»* «i bSelJ^J****** ewjilll 


ItiS 


-5 


■:7 


c 
a 




fit Tt 


t~ 




M •" ^! 


bl 




« 




v»# 


a 


3 


£ 


- 
- 


e. a 

as a 


■o 


tSatJsa tt.a j= .c »a .£ .2 .a a ecfitc^*^^ 


j3« 


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- 


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JS 


tlA 


■* 


jj ,2 -3 .a (x-a .s .3 .s .e .3 .c "a or £ 1 -c .a .3 .= 


■=.s 


~ 


j: 


* 


a 


J3J3 






"■a t£ 


A 


1 




JaJZ 


a a to £.3 tS tl u et ii tT bod — -= * "a C* M * t ' 


C" 3 


tZ 


a, 


tx 


a«fio« 


■H 


^-0 


j« a 


a 


ba 




s 


a cl 


1 


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«— 01 P! m « B5 PS « 05 « tc 1- M ffl Tl ^j « :^ s_T :t 

66 6666666666 66665c a a 


a o 


PS 

6 


5 


ST 

6 




65 


5 
i 


^ i -^ C ii ii u r r* 71 '^ V S ffl <i 4 i t' s w 




in 
6 


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8 
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3 
a £ & Jt ». 

iiiisiiiiifiililiili 

li-lls §l-&IIi life If fill 

a a BBS a = =.=■= ^'"Esisj' 
OOOO^OCOJO^PQKfcCra-- 


| 

a 

■/. -= fei 

t. - el 

r a 

: c; o 
^*- 3 

811 

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a 

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H 


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| 

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a — 
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a _ ~ 
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C-M:;7. E-. SSOSSjujS ^ K DD DO 

■^ w»ioioocre>iM'Tiffi'r_,z:rf — — 


st: O 

si 
— ^ 


CO 

fa 
H 


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7, 


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s 


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244 



TELEVISION ENGINEERS' POCKET BOOK 






3 I a a a I I I a 1 | | it | *! | 



I I 



St tL a i s a a 3 



I II II £<8l £dl I «««<■ I 



J3 a 5 -J* a 



I =i 

I 12' 



1 I 



#a*2**«3**233S* 




* I ill J I *&$ I $$$$$]$$# . faa J I a-; I 1 JL 



a"3 



«5(»fi(»tMajaxj:rtf J 3£jj\ s ii jeiM(S( B^|| ea* I I SL 



* I »J «*^« ** I ««4« j* 4 j .a . « 5„ V| | 4 



MXX^&&&£& = j S ZS£H# ~aMXM I «J3 I j= ^ 



~- i Jdi ^ii i iJ^iJ i 










§ II 

filiiilifili bun -•** 

~ 3 3 



« = ts = o9 a 



IfffiIHlIliI?33ii35i3§ 8§ 



^A«i:i:- n 3 £ 1 3 o => a o 3 . '"t « .s -; •*: ^ ■-' -• Sf-*hw. 



Eh 









la 



li 



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a - 
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NT 



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PS fc 



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4-1 



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P^4X| P4P4A4 



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^fa^SHfeSHa l feC < C,a < aiP5oJK«.3a!Sa55Bc : i[-&D!!-'S 






VALVE DATA 



245 



A 5. S. S. £.0 , , . , ™ . , a 05 es 01 , , si o> . , a ca ei W oc , 00 00 «j e> « 



MM 1*UUI«M U*M M I M I 



1 I 



* I M I aaalaaMlaaalMMM 



U Q _ O « 



■a._-JA(^J<.2_-.2----^--- a- 



I I I-"- ££$-a£$A*x.m* ImAJ^M"*^ 



1 ilnJUvai iJ4A3 i±3 1 Uiii 1*3^**** 



JLjl 

7. .V. I / 



a 



a I I b. S. S. £,« II i- "a S..3 .= js d j= .a a I «,a.O ,« a «.3 \? (Jw'a.a.a 




% af- I AAJ3 I J=«a I M AMa I I j-C&Ve *-=-= 



II |-a M*M$M 



Mm \ZTm 



u u y d y u* I _'Jdu& I — _ & I £ , 

J « .J J ~ .H * I flj JjJ J ' = — * » ' ■' 



■tfl I J I iJi lii'l 1 = : .llS I mmMmm tE« 



MOHrlOB«»Ol"HBOn»BBl»ffltlN«»K«n»«MiirtHFi|H 

c^eccciini-iieeoiocoiiciosooioeoiec 



O0>s"*«mooooo«ncoooi;oo03; loo OOooOOO© 
»HAMioMnot'cioii-(«o»i««isipao66oMia'fi'-r" 



I I 



~ jV, id iUr t- T7 l< ' S '- '- *3 '— 

T - CJ O 1* C f ' C T^ - 1 ■*-* T; *-* 

iiillislslli! 






eIeIgh 



jt is S ft 






3 3* = 






h R ^ - L ^ u 



i L. 

■5 ? 



" ~ T IT .r. 






et ■" ^ ^ S'^^'^*-' 

^ "f " ? flj*s*r'r*7: 



CQi3f-.PF-f5«CC^!-HiN^|H«"-lC5C^C a C3m^j-l2'CSE", 



246 



TELEVISION ENGINEERS' POCKET BOOK 



z <~* *".<<<< 



g en oo » oc oo oo oo ymsi-r.* r. i - 



II I I I Id I I I I I I II 



I I I I I I I I II 



*S I I I I I I I I tSl d Si II 1 I tStgjdjtZl do I 



x.3 x aaaaa ^sxtSldj * i .*edj=iIfS«Se5iZs.je5. 



" .' W » r. "O I 



"tSc So oe t£ t£ :* t» S.jntSo;!* «"= i .* £ as d 



- t a: 

.= .3 J (TsEsEtStS *ss ".s es a d ,= is «3(gt« «*— .= .= ,= .3.= I .sic 



d -- : ".- : $3 I .S--S- «» •=- (8«Sa & 



taUS.a J3 js I .= e! J3 j 



^ -4 J 



M C sB" s£ 4 cSl^JS^d Jd^ d <«.= ui Jd J4 JW M id ^4 I ,*.3 



tot* c a «e a « a suit's at c* ^.e^dbSaDecbobi; or a S.'^ 



«! S -= » -= •CdA __'.3 J! :j*.x a tStS d tl.3 -* J* ja M J4 bo I = J» 



oo o ooooo 



66 



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OO O 1BCOOO 

ci p-i — ci *r -^ ■* 



tb S3 e> o 6 t"~ ~* 6 6 s o 6 5D 



1 1 



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a> «o i sj o c> c? 

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w . „ _ w #£• *B U 









1- 


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1 




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VALVE DATA 



247 



i 


- - <*] •- 

p. i- 1- , 


1^ r. c; -: Cs C: *. Ci 
^! fS a s; S B fS S X 


,a»i>i> ■«) , i- <Xi oo oc cs e» cs = , , 


| 


I 


1 1 1U 


d 1 ! 1 1 1 1 1 


dd Id 1 1 1 1 1 1 1 i 1 


3S 


1 Id 1 


. 1 <2k ti^wJS 


Id ill II 1 1 1 ItStStfd 


00 


1 1 5. I <3 


<£ 1 .S^< MtEttsEc 


5tJ 1 1 1 1 .c ^ l .= .= .c £ so £ sKe 




tStSteSja 




isle, . M X S,M i! AS 3 cS = C J3 


j «: :' r 

IS 


1 -«•■ 1 ■= 
ii._- <« 1 01 as j: s 


1 ._; 1 a 1 — SZ 1 •DDbCBttf. CCV. '£ 1 


KB 


<3 *fl X GE fS 


*Id£j;f£££- 


1 ! -an* t 

ttx 1 j« ;ij! ttattii box A * JB a 


■9" 


A £ — J! *i« 


1 AMAMAAMA 


1 .= 1 J! ^ tj ao (iTx i tl t2-= X x x j« 


m 


£«i«J3 I 1 




Of 


e* 


J! M "tCM X 


^ it ti'tt ii ■£ a ti. t~ 


x J.* «i«ra jiii'j>t:l ;7-= 


— 


si el's be r 




| ^JsTH « X A 1 &S J X J< A .X i gg 


1 

1 


i 


IBM 

;* *« -r :■* : . 

66666 


:6i666cii 


<7 « '!S U5 K» 

^•-HP;nRnUR»0;ci?icC7;7;n 
ti iicii ii; ii; :6 : z 6 


s 

3 


to tS SO tc *P 


rt ;c rt rt rt rs & to :- 






a 
S 

s, 

1 


M 

3 1 5 6 r 

St 5 c c t 

•"! 3 ft .s c; s c = ^ • 5 --z 


- ££& 

- ^is 

= BBS 
t » S fi 
JB ft -3 & — — e 

" — U Ql O P G) V 0.,'..'b & & O 

j. — *r ""t:^^^""^ ■ t " ^ 

1 — = ~ = C — C 3 = -3Z"3 

frgC s IgtsSSSIIIIig 




"1 


^0 *£. 30 ta 

S= O'O'E-' 05 


5' m « r- P I~ w f- - 


/^ tM rt f m "t c; ri sc 



248 TELEVISION ENGINEERS' POCKET BOOK 






isiiijiuii.ini ii 1 1 1 1 1 1 1 1 1 1 1 i 



I 1 I I l*«l II I II I Is J I »al I laiaUs I 



J*MMjSMj£'k^z:x:MMj;jzjz£ %m m-°j: « «£ I eS I 




I I I T» I a a »\o£ I I MM I b & .S I I'teW** S'? I *** £ £ 



ec to to a tt.= ;."'e86tttiss 



.^ jg et ~ — 



1**1 



A «.s «.3,s 



1 Sli* 



U,= — aMoiU 



I* Vao I — - £ J-ii 



jrXAfj 



•n 



a s a'tca^i* ""ichca I ***)M tS m a ^sJa'cj'^j^Jiti c 
.7 « 



j^i'sj^'M'-ias s^^e 



W'aM I 



ao-W bii-M -j \- a 



[/itn^^^V^^^^ 1 *t£*to I 



a <srfi izMszxs; a u.2 



O <!SO0 









*8b 



c -S S 2 '5 * n "S ^ ^ £ 

a> &-I.SS.3 £ fiSJ'Sfi, 
"3 • •*•= £- — "9 — ~ p. a 



:— 3 
■ o o 



F-i o Eh 

as iiwoota^ioijct^i^o 



r; B «! loss© » & & » <p 

llliililiii^l s 

?IsilllI**|||| -si 

::"co:o»t^3si , i: "Ci 



■* <o S? 2 55 o '- ■* » « 5 s so t- co H 

tp <p W (P I- I » l- " » J". OS S"- C» Ci Cl r* 



VALVE DATA 



249 



fC mr^SosSoo cs » = =s 'a s ~ s '- £ « , ,. ., . '£ £ ,,,.. 2 i> 5 5 



[ I I I I I 1 I I I 1 I I I 1 m a 1 [ I I a 1 a I a = I I I 



I I I isi IJI lilll«s aid! I I I I I Iddil 1 l 



I a tl • ! .= V. ^ ^ i< *: ^ %i I -* ." tS.5 I •= -^ -^ -^ ■* ■= =2 ^ ■* * M 



- tua M«ci«» ■ -J3 od tt i* (» a Si" jfijSJi^fi-* jT.^ .^ - — 

.8 - £* tf«-S £ I «V«** I f < I S m^»\ I I *.i.i I I 



t£ m MAM "<xjs aotx^x;^:^^: x: dla j; t»"a eEM^tTj;— on* e 



Si j3 (Sj:^ »«.!3 £a,cj3^£~ « I *JnSMi»*t»i:--s eS I I 






e. 
ja i, ^^w^a^ h*aVa I S ^ Ij3«*<l I I \*$hX I i 






5 9 



010000*0 o'ti sj>3c ooooeeoosoosoona 
'ioBoieeseii ^ 5 2 *' i 2? fi S?iSS « «S S 



C) i-< «»nniH 



1 I? 



fe I 






J**— 






45 *9 49 *v S ^ 



P oS^-Kc3-3C0003=iO~ B 0.0,5=,Sc3 



III 

ass 



^i^apSSpSKH 



250 



TELEVISION ENGINEERS' POCKET BOOK 



»ss o> e» «. cs , , es si * c-. si S . • 



III I I I I m ! I I 1 I * I I I « s | «. « 



StS« & as a 1 rZ t£ £ t* £ I I I I I I .s | | 



-£«•■ 

M* 



P 3 tt . . . — _ 



i&St <SSat^s^-=cS«=ay-||j;. 



22 2 *Svui<$£$g IV* I I U I I 



— -c -^ — •= <fi -= £— -= -c ,4 x sjl| 1 e£ sa t5 * t» x 



xxx xx^xtZxxxxx 



C eC ab tt, ti Uh u. 




60 te Cl tL t£.i i Xtlt4".|^L i'XXXX 



- S* ,, .'j«Si ( i,^«i«l - jH I I I I I I - I 

MM 



rt cc r: « k p; xy rt ro rt ;,: st r; « sc p? t* M c* SO W* c. 



"? T t «^^0— w«SOZZ2 Z- C © « is rt c-3 
~, c. — . NftiM^isftoi^rtB sj .^ ,-; rz \c A c 




-> « =S 3, 



- St -f-i. = "•- ~~~ - 3 " "r~ — £"-/£■- " S 1 




VALVE DATA 



Table 15.2. — Valve Equivalents 



2SI 



Tfpt 


I'.itiih-tihnU 


Tijpc 


Bgvivalenta 


AZ31 


1 143 


B7.80 


6V4 


B86 


1382*701 


gW*-800 


U18/20, 451TT 


B8S 


B8N7GT 


(xZ30 


R68.6Z4G I 


]Jlf>2 


BCC81, BS09, I2AT7 


uz:i2 


SV4G, -jiKU 


B30S 


BOC81, 18AT7, B16S 


ll.\:iOD 


PCL8S, t«A8 


B819 


PI i 84, 7AN7, 80L1 


HTB8 


\ I.Stl] 


i«29 


BO 88, ISAU7 


KT'H 


N147, BAdfifi, CP25 


B88S 


!■:< i s:i. 12AX7. 6Li:: 


£48 


6J .">( ; 


Ii7 ID 


BOOBS, 6AQ8, BUS 


l,MI!l 


i . L8S (near), l^l'LlS 


i ::-.".i 


(1 SOLS 


LX152 


BOL80, 6AB8 


hi 


T4I> 


UT808 


POLS3 


i>7 7 


KIlDl. l)l)G, 0AL0. CD2 


EJ5819 


POF80, SAB, 0A8, 8001 


DIM 


i;i'.;m. nun, halo, i>77 


LZS39 


PCF80, 80C1 


Dim 


l»77. BBW, SALS, til v> 


N78 


BBJS 


1 H177 


BBC60, (iA'I'O 


NU5 


LOPia 


1HT71S 


EABC80, ti\ h>. ci.dis, i;TS 


XJ17 


6AG8G, KT.33 


BA60 


shin. fil»l 


NKiii 


KLU, GfK. - ., B7IT 


I-IAUIWD 


DH719, 6AK8, t;!,l>l*J. 8OT 


\l-M 


BL48 


HAF42 


w h1.-.o. W7T7 


K15S 


trS89, EL81, SlAfl 


BBM 


0Hfit;T 


Mr,:; 


N':i)>U, PL83, 15A6 


BBS] 


1)77, U132, DOG, BALS. GD3 


traos 


80P4 


KBC33 


1 )]|«:i. hill 17, mil. r,g7i; 


\ :;i id 


N188, PL88, L6A8 


KliCIl 


oil I uu, WV7, (ii,ii:'„ liaimT 


N SS9 


NI34, PI-82, 1CA*. 


KKC90 


hi 177. 8A*M 


S8S9 


M. ■■■.', PL81, 21A(1 


KJtFKtl 


WD709, ZD15S, OXS 


\ 8(9 


I'l.Nl. N'152, 21AB 


BBF8B 


BDC8, BFD1S 


n:;i',d 


WWPia 


KC081 


l!l.-i2, BB09, 12AT7 


N879 


ri.si. i;,i»(,»s, :mri8 


BC0S2 


|:;;.".i. L8A1T7 


BJ708 


i:i.si. 8BQ8, 63*10 


Bl 'I M3 


li:i:v!i. 81,18, 12AX7 


N'727 


BL90, 6AQ0 


JC( 't.:84 


BOW 7 


OM4 


Kltrss. hill 17. inn;:; 


ki i ■*:> 


It71!i, BAQ8, BUS 


iiMii 


BFS9, VVM7 


B0G91 


i;.li; 


OMW 


i ill:;.*, or Km :;.->. XM7 


Kri-'sii 


BHL8 


VW.r^u 


D.VKs 


KCF82 


e i rs 


POC84 


H:;lD, 7AN7, "<iLl 


BCH8S 


OM10, m;!\i. \i 17 


PC08B 


BAQ8 


E0H4S 


\\:,n. 8010, Ml", 68TB 


I'Cl'Sn 


LZ8I9, BA8, 9AB, 8001 


E0L80 


BAB8, I.M.VJ 


PCP88 


BUS 


>;t;L82 


BBM8 


PCL82 


HK809, I6A8 


HF30 


(IMC. WM7.CK.7i; 1 


POL88 


LX3U9 


KFI1 


Wl.-Mi, li-jVI'. CFtTi, CCIfi 


PL88 


V:i(iS, 25Kri 


BF43 


/,]:••>. BFI8 (ucnr) 


1 PL81 


N152, 21AI5, N8S9 


BF60 


83SFT, Z90 


PL88 


XI.'jI, X329, I8AS, 30 PI 8 


BF80 


/.I.VJ, Z7IH. liltXG. CBW7 


PL88 


N 188, N309, 15A6 


BP8JS 


\V7l!t. CI!V7, til- ID 


PL84 


x:'.7D, I8DQ8, 80P18 


H F89 


8DA6 


PT88 


i:2i»i 


BP9] 


BFB, /.77. BAK6, 6F18, 8D3 


i'\'8U 


i;jr.2, tJ809, idx:; 


BF9S 


\\ 7l'7, I11U6 


PT81 


ii:,;;, i S89(n88r), 177,3 


BLSS 


6AQ6G 


V\*-> 


D154, 0819, 18T8 


BL38 


6(.!X8 


PZSO 


KM 


EL-41 


N160 


1112 


BYfllj .-I 81, i i::. I'l.M. 8X2 


BL42 


NISI 


1 : i »-. it-.' 


its, trsi 


HL81 


CC.18 


1152 


i;/.;;i), ;>/,n;T 


KLS4 


B709, BBQS, fiL'15 


SIT, 


J4P9I, Z77, fiAMO, 8P12, 81).". 


KL90 


_N7L>7. CAC,i.-» 


<n;i 


KY.-.l, Ills. Ti:;. fl.-.l, i:\-j 


BUS] 


6(;iJ6. 7 DH! 


OSB 


V-17 


KY.-.l 


B12, sr<;i.ri:;. rir.i. r;\ L ' 


i 211 


1T49 


KYSii 


88 l" 


1-31 


2.-./.-U1 


BZSS 


DU7, 6X5OT 


r;s7 


Mill. 1T2 











252 



Ttipr 



i 43 
U49 

T7S2 
ril-i 

i-ii;, 

TT147 
TT151 
DIBS 
l"153 
T154 
0188 
1T2AI 

craw 
rrso9 

DJ1B 

r:iL'!i 
CT3M 
1*104 
0AP4S 

UIKJ41 

t" IS FSB 
00C8B 
n '11-12 
1TF41 

II 4 2 

rvji 

VI.K61 
W718 

W727 
« 72D 

w ::;>.> 

A 1)1-12 
M D1«0 
Wl)7u;t 
Kffl 

7.7 7 
7,1.1(1 
7.152 
ZSM 

Z7l!i 
7. 1 1 1 52 
•IV 4 
BABS 
BALfi 

liAMfl 
8AQ8 

a ids 

BATS 
6BA6 

HHW7 

B1JX6 
BUY 7 

6012 
ticue 
cm 



TELEVISION ENGINEERS' POCKET BOOK 



Eqttimltlitx 



EY51, B12, SWBl, BX-J 

H26 

5TT4G 

A 7,31 

run 

BZ88, U70, b.\,k;t 

KY.-.1.K12, 8TJ61, l-.ja, 6X2 

PYSd, laxn. L'aiisi 

FYs I. i :;•_>!>, ]7/.:; 

PYS3, T3I1I, l!iV:i 

FYS2 

PT81, xm». 177.3 

PY88 

PY80 

PT8S, IfTS 

PX81, D35J, 177.8 

l"l!il 

i i ii 

WM 12, I2S7 

Mills. DB148, I0LD8. 

Ill OUT 
17CK, 1711)1)1' 
HI 09, 1DLI4 

xi «, MK7. iirni 

Will'. H'lVI' 

SS142 

X142, 45AS, 451PT 

ri42, ::iisr, r.i \:; 
HVB8 

BF86, r,[tY7, 6FIU 
BP9S, SBA6 
BF8S, 6BY7, BFlu 
BF18 

F*AF42. ti'^7 
F.AF42, 6CT7 
BBF80, ZBlftl 
«.l7ri 

F.FSU. Sl'fi, BAMG, BF12, 8113 
BF43 

KFHU, 7,719, GBX6, 611W7 
80F5 

BF80, BHX6, Z152, GmY7 
F.HFS0. \VD7f)U, B\s 
CSZ32 

P.CLSO, LX152 
F.I I Ml. D77, J.) 152, 1»|.)6, 6D2 
DH719, BAB080, BLD12, 
818 
KF!)1, Sl'fi. 7,77. BFI'J. Sl>3 
Kf,HO, N727 
1(719. B0C8S 
IU177. HHC90 
F.F93, W'71'7 
8D6 

KI'SI). Z71U, Z152 
EF8.1, W719, 6F10 
1VHSI, X71M, iSA.Is 
KL831, 7D1u 
BA0O, BDM 



Type 



BqttieatattS 



BH2 
BFB 

torn 

8F1S. 

c,|.|'.i 

tSFIill* 

BUG 

8J8 

6.1 6 

6J7QT 

6L12 

fiU3 

6LD12 

6P28 

BS \ 71 i X 

B l F8 

BV-I 
BYY2 

i; ::ti|,2 
7A\7 

roe 

TV l 
>\^ 
BDJ 

•IAS 

BD6 

nxs 

10(3 

n»Fi 

10P18 

10LD11 

10LD18 

L0P1S 

L0P18 

I1AT7 

ll'AI" 

12AX7 

12SN7GT 

i.i ai; 

16A.1 

16AS 

177.:; 
lux:t 

m :; 

21 AC 

SUM 

251..; 
25Z4 
8001 
SOPS 

aur.i 

3l>F4 

30F12 

3uP]B 

SUFIS 

B8XTT 

54 K 1 ^ 

IKl'i 
807 



D77, IH)6, KTSSil. 8AL8 

Kaw 

HP81, 8P8, 7-77, BAMii. BBS 

W739 

BBSS, W719, 8BY7 

BBP88, 6 DCS 

1>6S 

LOS 

KCU91 

/fiT 

1I71H, J40C83, OAQH 

l'.:;:iM. i-:iv.i:t; 12AX7 
1)11711). BABC80. 8AK8, 8T8 
KTB1 
BOB 

scares 

BZ80 

l!12A 

B789 

USlfl, FC0S4, 3til,| 

X14S 

i B2 

L7,S1!), PCF80, HAS. m I 

BF91. Sl'(i. 777. 6AM6, 6P18 

1,7.:; l;i, Fcfso. sas, :;uci 

BP82, W77, Vl'8, Gf:Q6 

POF88 

X I i- 

Z14S 

Wll!) 

I l-l.l 1.1 

DH14B, tTB081 

X14.1, VI is 

N 1 1 D, I TLH4 

USUI). KrcM. It 1.1 2 

B839, BOC82 

B888, B0C8S, fiUS 

B8fl 

M53. N3U!), 1'l.s:; 

XI 54. VSlMl. I'l.M'. :il»Flfi 

FfIL82, H.X303 

FYttl. ('153, I -3211 

FY. Su, 11152, 1*309 

PY82, X7134, F319 

M.12. x:;:;'.i. N859. PL81 

FLSl (ueftr) 

kt:;2 

U31 

LZ318, FCFSU, SAS, HAS 

7320 

K313. FCC.*4. 7AX7 

X*3l)8, l'l,3« 

\:;B!i 

X154, N32B, FLS2, 16AS 

X37D, FLsi. ir.iig.s. lions 

<i/.37, U54 

(;7,32 

BPSO 

QV05-25 






[SECTION 16] 

COLOUR CODES 

RESISTORS 

The information on resistors given by current colour coding 
systems includes value, tolerance and grade. These characteris- 
tics are indicated either (1) by a series of three or more colour 
rings which are read from the end of the resistor towards its 
centre {Fig. 1); or, alternatively, (2) by reading first the body 
colour; secondly, the tip colour; thirdly, the spot or band 
colour (Fig. 2). In system (2) the fourth colour (tolerance) is 
indicated by marking the second tip but, since the colours 
normally differ from those used to designate value, no confusion 
is likely to arise. 

In each system, the first colour to be read indicates the first 
figure of the value; the second colour gives the second figure of 
the value ; and the third colour gives the number by which the 
first two figures should be multiplied in order to arrive at the 
true value of the resistor. The fourth colour shows the tolerance ; 
the accepted tolerances being ± 1 per cent, ± 2 per cent, ± 5 
per cent, ±10 per cent and ± 20 per cent. Where no tolerance 
is indicated, it may be assumed that the tolerance is ± 20 per 
cent. 



■ Mil 
t V T t 

A B C D 



F 





FIG. 1 




Fid. 2 




CoUntr 1st Figure (J) 


2nd figure (B) 


Multiplier ((.') 


Tolerance U)) 


Blaok 








1 


— 


Drown 


1 


1 


10 


±1% 


Bed 


2 


o 


100 


±2% 


Orange 


3 


3 


1,000 


— 


Yellow 


1 


4 


10,000 


— 


Oreen 


. 


.1 


100,000 


— 


Blue 


6 


6 


1,000,000 


— 


Violet 


7 


i 


111,(100,000 


— 


Cirey 


8 


s 


100,000,000 


— 


Wliitc 


9 


9 


11 H)U,I H 111,111 M 


— 


fJold 








0-1 


±5% 


Silver 





— 


0-01 


Lit'",, 
±20% 


No colonr 


■ 


— 


~ 



253 



254 



TELEVISION ENGINEERS' POCKET BOOK 



Grade I, high-stability, composition resistors aro coded as (I) 
above, the- grade being denoted by either a fifth band of salmon 
|iink, or the body being of that colour. 

Examples. — A resistor with a blue body, a gray tip and an 
orange spot would have o value of 0S,()Ou ohms with a tolerance 
of ± 20 per cent. The addition of a silver band or tip would 
indicato a tolerunco of ± 10 per eont. 

A resistor with four bands of colour, the end ono being orange, 
tlio next orango, followed by brown and gold would have a 
value of 330 ohms with a tolerance of :r: 5 per cent. In this easo 
tho body colour would have no significance, unless salmon pink, 
which would indicate a Grade 1 resistor. 



CONDENSERS 

Although many condensers continue to bo marked directly 
with their value and rating, several systems of colour coding are 
also in use. Thoso differ according to the typo of condensed at id 
tho extent of tho information to bo convoyed, though in all cases 
tho same basic code to that used for resistors is adopted, except 
for the 01 and 0-01 multipliers. Information that may bo 
shown by colour coding includes: valuo, temperature coefficient, 
tolerance and voltage rating. In addition, the connection to tho 
outer foil of tubular paper condensers may be indicated by a 
band of colour, usually black, being placed on the casing close to 
tho appropriate connection. All values aro colour coded in 
picofarads (to convert to microfarads divide by 1,000,000). 

Ceramic Dielectric. — These have a distinctive end colour, do- 
noting tho temperature coefficient, followed by four colour dots, 
the first dot being that nearest the end colour, tho remainder 
being read in order towards tho centre. The tolerance is indi- 
cated in percentage for values greater than 10 pF, but directly 
in picofarads for lesser capacitances. 





Tip 


\»t Dot 


2ml Dot 


Brd Dvt 


4th Dot 












Tolerance 


Valour 


Temp. 
Cottff. 


l*f 
Significant 


2nd 

Significant 


Mtiltii<lii-r 












/ i'jitre 


Figure 




More than 


Leu than 












1 "/-/■■. 


10 pi-'. 


Black 


OT0 








1 


±20% 


+ 2-0pF. 


Brown 
Red. 


X0.1l) 
NOSfl 


1 

2 


1 
2 


1Q 

100 


± 1% 

± 2% 


; "1 pi'. 


Orange 


M.'MI 


.1 


;; 


IjOQO 


4- 2-5% 




Yellow , 


.V -22> i 


4 


-t 


lli,(]OU 







(■reen 
Blue 


Nsao 

XI 71) 


5 

e 


6 


— 


± '»% 


| 0-5 pP, 


Violet 


N7S0 


7 


7 








tirev 


roao 


S 


8 


0-01 


■ 


±0-25 pF. 


White 


FIDO 


U I 


a 


0-1 


±10% 


±1-0 pP. 



COLOUR CODES 



2S5 



Ttthidfir, Metallised -paper.— Tho values may bo colour coded 
in picofarads, indicated by three dots, having (lie same signifi- 
cance as in the third, fourth and fifth columns in tho table for 
ceramic dielectric condensers. 

Alternative Methods. — While tho abovo systems are those 
recommended for currant usage, several other methods may be 
met in practice. For example, one colour only may be used to 
denote tolerance, two colours to denote tolerance and voltage 
rating, threo colours to denote capacitance in picofarads, five 
colours to denote capacitance in picofarads (first tlu'eo colours), 
tolerance (fourth dot) and voltago rating (fifth dot). The order 
in which the dots are to be read is sometimes indicated by an 
arrow, but in all cases is from left to right, the first dot boing that 
nearest to one end. 

In such instances, tolerance and voltage rating are coded as 
follows : 



Colour 


Tolerance, % 


Voltage Hating 


Black . 










Brow it . 








1 


ion 


Bed 








2 


201 > 


Orange . 








:i 


SOO 


Yellow . 








4 


400 


(ircen . 








5 


B00 


Blue 








e 


600 


Violet . 






7 


700 


Orey 

While . 






S 


SOO 






<l 


loiii) 


Silver . 






In 


— 


Gold 






' 


- 



Coiling of American condenser* also differs slightly from that 
described above: the KM A three-dot code is used for condensers 
having a tolerance of 20 per cent, the dots indicating the capaci- 
tance in picofarads; the EMA six-dot code gives (top row) first. 
second find third significant figures: (bottom row) voltage rating, 
tolerance and docimcal multiplier. American fixed ceramic 
condensers havo a broad band followed by four narrow bands or 
dots giving temperature coefficient, first significant figure, second 
significant figure, decimal multiplier and tolerance, this system 
being similar to that described for British condensers of this 
type. American war-surplus mica and moulded paper conden- 
sers are marked according to American War Standards or Joint 
Army-Navy specifications. These marking are similar in 
appearance to tho EMA six-dot system, but the first dot of the 
top row indicates type (black/mica, silver/paper), the second 
and third dots give first and second significant figures, while the 
bottom row indicates characteristic, tolerance and decimal 
multiplier. 



INDEX 



AiiSMKiTioN trap, 137 

4« intermediate frequencies, 199 

Adjustments, mechanical picture, 10 1 

Ai'rinl sain, 131 

Aerials, J 30 et sea. 

Band Hi, 188 

Installation, I in 
Aircraft It utter, 140 
AU>a intermediate freqwaafeg, 190 
Alignment, 171 tit tea, 

faults i», l«*i-7l 

of tuners, 197 

response curves, 1 76 

s wit eh tuner, '217 
Aluminising, 222 

Ambassador intermedial c In-qiiendas, 
109 

Anode damping: devise. 2 is 

" Anti-patterning " unit, 98 
Argosy in tern icil in If frequencies, 199 
Aspect rutin, 12, J 117 
Attenuators, 189- 4(1 
Automatic- contrast control, 11m 
Automatic frequency control, to 
Automatic gain control, 51, 180 
gated, 52 

mean level, 51 

" syne, cancelled ", .". ! 
Automatic picture control, 51 

" Hack porch ",12 

Hairtt intermediate frequencies, 200 

Baud l/I H receiver circuits, 177 

Hand [.'III conversions. 92 et se-i. 

Hand-width, 17, 81, 1117 

Banner Intermediate frequencies, 21)0 

ILIUV 

television t.ransnii tiers, 20 

tent card, " V ", 100 7 

translator stations, 21 

V.ll.F./F.M. stations, 21 
ilcaiu centring magnets, KM 

HffthtYiY)! inter diate frequencies. 

20(1 
Blocking oscillator, 41 
Bowjeetfm Intermediate frequencies, 
209 

Brimar cathode-ray tube data, 230 
British Television System, 1 1 
Bush intermediate frequencies, 800 

Cathode-ray tubes, 219 et seii. 
bases, 22s -9 
circuitry, (units to, 168 
equivalents, 286 
la 11 Its in, I.-.m 
handling of, 221 
projection, 80-2 
replacement, 230-7 



256 



Cathodem cathode-raj tube data, 880 
Centring, (in 

Champion intermediate frequencies, 

801 
Channel selection. Ml 
Coincidence detector, 57 
Colour codes, 253 

capacitors, 851 

resistors, 253 

television, 08-73 

tubular-metallised paper, 255 
Columbia intcrniediate frequencies. 
801 

" (' para tor " valve, 58 

Component deterioration, 163 
Component test bridges, 1215 
Contrast, 107 
Controls, user, 106 
Conversion, Bund 01,91 etteq. 

problems, 97 

saperheterodyne receivers, 05 

T.K.F. receivers, 91 
( 'ussnr: 

cathode-ray tube data, 230-1 

iuterniediate frequencies, 201 
Cramping, 102-3 
Crystal calibrators, 128 

Damping device, 189 

D.C. inverter, 70 

D.C. restoration, 50 

Deeea intermediate frequencies, 202 

Decibel, 131 

Defiant iuterniediate frequencies, 202 

Defection, 880 

Deflection tubes, wide-angle, 223 

Detector: 

sound, :JG 

vision, 33 
De-saturated transformers, 45 
Dint benny interference, I fe 
Differentiating circuit, 19 
Dipote, LSI 
Directors, 133 

Dual-chat I sound receiver, 39 

Duutitron intermediate frequencies, 
898 

Earths, 191 

Edixirtin-Miizitii picture- tube data 

231 
Efficiency diode, 44 
E.H.T., 49-50 

laid Is in, 168 

measurement of, 127 

precautions. 109 
Ekco intermediate frequencies, 2U3 
Electrode short-circuits, 220 
Electrostatic focusing, 223 



INDEX 



257 






eTmtMMM cat bodc-ray lube data, 231 - 
2 

ISmitrm cathode-ray tube data, 252 

English Electric: 
cathode-ray tube data, 2:42 
intcrniediate frequencies, 804 

Etronit: intermediate frequencies, 20 1 

Feeders, I3«w. *vy. 

Ferguson intermediate frequencies, 
204 

I'l-rntnti: 
eathodc-ray tube data, 232-3 
intermediate frequencies, 205 

Field-strength pattern, 131 

Field strength maps, 17 et seq. 

" Flare ", 173 

Flat tube, 71 

Flywheel synchronisation, 55-9 

Focusing, 2211 
electrostatic, 223 

Folded dipole, 134 

Frame-grid valves, 80, 88 

Frame-synchronising pulses, 13 

Frame time-base, 28, 83, 155. 102 

Freak propagation, 148 

Frequency changer, 31 

Fringe area equipment, 142 

" Front, porch ", 12 

Fronf-to-back ratio, 131 

(ia ted A.U.C., 52 

(i. ICC.: 
cathode-ray tube data, 233-4 
iuterniediate frequencies, 200 

Qhoet linages, 142 :i 

Half- wave dipole, 130 

Hartley oscillator, 31 

Heterodyne interference, 146 

Highlights, loss Of, 173 

tl.M.V. intermediate frequencies, 207 

H.T. supplies, 88 

LI', alignment, I Si) el veil. 

I.F. an 1 pi location. 32 H $&/., 179 

I.F., choice of, 32 

Ignition interference. 111 7 

Impedance, aerial, 130 

Impulse interference, 144 ft set/. 

Incremental switch Band 1/1II tuner, 

J 80 2 
Independent Television Authority, 22 
Indoor aerials, 134 
Insulation testers, 120 
Integrating circuit, 49 
Interference bv television receiver.-., 

149 
Interference, causes of, 144 et seg. 
Interference suppression, 35, 37, 145- 

B 
Interlace faults, 157 
Interlacing scanning, 10 
Intcrniediate frequencies, 180, '99 

etteq. 
Inter-stage coupling, 51 



linirtii intermediate frequencies, 20 7 
Ion-trap magnets, adjusting, 104 
hm-traps, 221-2 
I.T.A.: 

transmitters, 22 

test card " ". 1(IH 

Ktiistrr HrttHtirx intermediate fre- 
quencies, 208 

lane flyback cireuilry, 5ii 

Line output stage, 1 61 > 

" Line Hinging ", 172 

Line-synchronising pulses, 14 

Line output transformer testing, 103 

Line Mute-bases, 41 et xej., 84, 150 

160 
Local oscillator, 30 
liow-cnusslon tubes, 220 
Low- frequency response, 108 

McCarthy intermediate frequencies, 

208 
SIcMichael intermedial c frequencies, 

209 
.Mains-connected chassis, 109 
M a rcvnipfi one intcrniediate f re - 

quencies, 200 
MtuUruMo intermediate frequencies, 

210 
Mulching aerials to feeders. 138 
Mazda cathode-ray tube data, 224-5 
Mean level A.O.C., 51 
Mechanical picture adjustments, 103 
Metros! Is, 50 
Mixer, 30 
Milliard: 
cathode- ray lube data, 834 
intermediate frequencies, 210 
.Multi-channel selection, 20 
Multi-electrode guns, 223 

Multi-element aerial arrays, 184 
Multi-receiver installations, 141 
Multi-vibrator circuits, 12 3 
Murphy intermediate frequencies, 
210 

X.T.S.t.'. colour systems, 00 

Optical system, projection, 70 

Oscilloscopes, 121 else'}. 
use of, lf>2 00 

Pageant intermediate frequencies 

•211 
film intermediate frequencies, 211 
Pattern generators, 119 et sea. 
Pat tern log, 94 
" Peak white", 11 
1'eto Srolt intermediate frequencies, 

211 

I'hiirn intermediate frequencies, 212 
/'li Hips intermediate frequencies, 

212 
Picture adjustments, mechanical, 103 
Picture centring on screen, 90 



258 



INDEX 



Picture centring mi tube face, iHt 
Picture faults, HIB et W7, 
Picture-repetition frequency, '•> 
Picture transmission, it) 
Picture-tube salvage, 22.". 
Pilot intermediate Ernquenciea, 819 
Pin-cushion distortion, 82 

I'immrlp cathnile-ray t nbe data, 234 

" Plastic " picture, 173 

I'nrlnihfitr intermediate irctriif iiuios, 
218 

Power supplies, 49, !)2 

Pre-set consols, 108 

Priii ti'd-circuit receivers: 
general precautions, 1 1 1 
replacing components, 112 
servicing of, im 

Is, lit 

Programme Oompaniea for l.T.A. 
23 

Projection systems, 79 et *»/, 

eathode-rav tubes, 80 

E.H.T. circuit 88 

mechanical focusing, 88-S) 

mirrore. cleaning, »(i 

protective circuits, S4 
" Pulling", 172 
I'm- intermediate frequencies, 213 

Rttymond intermediate frequencies, 
214 

Reactance valve, so 

ttoceiver circuito. Band I'm, 170 

ttefleoton, 108, 132 

RegentuM intermediate frequencies, 

•214 
Resolution, 1(17 
U.K. stages, 28 
faults in, 1 ."1:1 
!!.(;.]>. Intermediate frequencies, SI 1 
" Kinging", 44, I Bo, I7L 

saw-tooth generator, 41 
Scanning, 10 
Sea rming linearity. 108 
Schmidt n|iticjil system, 7'J-8() 
Sensitivity controls, 102 
Servicing precantionfl, 108 atsej, 
Setting-up, KM et stq. 
Shadow-mask tubes. 70 
Shortcd-tnrii linearity and width 

controls, 4(i 
Silicon reetillers, 1<> 
Slot ai-rials, 1;U 

Su'h'H intermediate frequencies, 2i"i 
Sound: 

band-width, 86 

detection, 36 

interfere nee suppressor, 37 

output stage, 38 



Souiid-oti-vtsittn. 172 

8pgneer*We8t intermediate fre- 

qneneies, 2 1 5 
Spoi inversion, 84, I4.j 

Star networks, 142 
Steering magnets, 1UI 
xtella intermediate frequencies, 210 
strmi Intermediate frequencies, 210 
" Streaking ", 173 
Subjective colour system, 71 
Sweep generator alignment, 1!):5 et 
teg. 

Switch timer, 184 

Switch tuner alignment, 217 

sync, cancelled A. G.C., 64 

Synchronisation faults, 103 
Synchronising separation, 47 et s*g_ 
I its 
faults in, 156 

" T " attenuators, 188 
Termination device, 187 
Test bridges, 12(5-7 
Time-base circuitry, II et 8#}, 
Time-base controls, i • i i 
Time-base faults, 160 

T-pad lor -iLiiial -j '-iterators. 12(1 

Transatlantic cable, 22 
Transformers, use of cables as, 137 
Transistor receivers, 74 

Translator stations, 21 
Transmitting stations, frequencies 

17 
Tripler, voltage, 88 
Trouble- tracing chart, 1(17-71 
Turret repairs, 168 
Turret tuner, 21), 184, 187 
constructional details of, 183 

Valve testers, 127 
Valve voltohmmoters, 128 
Valves: 
bases, 289 

data, 238 et wy. 
equivalents. 261 
V.H.F. f'.M. reception, 88 

v.il.K.-K.M. stations, 21 
V.H.F, frequency bands, m 
Video amplifier, 33 

faults in, 166 
Vidor intermediate frequencies. 210 
Vision detector, 33 
Vision interference, L02 

I i miter, 35 
Voltage tripler, 87 

Wh&t-Ibbettm intermediate fre- 
quencies, 217 
Wide-angle tubes, 223 
Wobluiliitors, 122 et tog. 









r A -H r i 

Valves 

Cathode 
Ray Tubes 

Silicon 

Semiconductor 

Devices 




FERRANTT LTD • GEM MILL • CHADDERT0N 

Te/ephone: MAIn 666! 



OLDHAM ' LANGS 




LONDON OFFICE: 
Telephone : TEMple Bar 6666 



259 




right through! 



Top-quality work has won for Belchers 
an honoured name throughout the trade. 
This is not achieved by chance. The 
men whose skills and thoroughness are 
displayed in every job they do are, 
themselves, members of a select team. 
And as such they receive every facility 
and opportunity to demonstrate their 
own high standing. It's the servicemen, 
above all, who earn the A-i Stamp for 
Belchers 







Head Office: 

59 Windsor Road, Slough, Bucks 

Telephone: Slough 24501 

BRANCHES THROUGHOUT THE COUNTRY 



SELENIUM RECTIFIERS 

FOR 

TELEVISION RECEIVERS 




Specially developed for 
use in T.V. receivers, they 
have a good life 
performance and are 
mechanically and 
electrically 

interchangeable with the 
original stacks quoted. 



Type 


Equivalent to 


Volts Input 
(R.M.S.) 


Current Output 
(mAJ 


SE14 


RM4 


250 


275 


SE15 


RM5 


250 


300 


SE17 


LW7 


250 


300 


SEI9 


LW9 


270 


300 


SEMI 


LWM 


250 


300 


SEII2 


LW12 


270 


300 


SEI7 


14A86 


250 


300 


SEI9 


14A100 


270 


300 



SALF0RD ELECTRICAL INSTRUMENTS LTD 
PEEL WORKS, SILK STREET, SAL FORD 3, LANCS. 

LONDON SALES OFFICE: MAGNET HOUSE, KINCSWAY, W.C.2 

TEL: TEMPLE BAR 466B 



2fil 



WINSTON DECADE BOXES 



These resistance and capacitance decades were designed 
especially to ascertain the required value of a condenser 
or resistance in «i port of a circuit, or to carry out 
normal test functions without the need for expensive 
decades of the /% varieties. 

i DECADE CAPACITOR BOX 

Range: 0.001 mfd, co I.I I mfd. 
Zero Capacitance: 50 pf. 
Accuracy: ±5%. 
Maximum Voltage: 750 v D.C. 
Termirals: Screw Type, 
Dimensions (overall): Height 3 in. 
(7,5 cms). Width a in. (20 cms). 
Depth 3j in. (9.5 cms). Weight 5 lbs, 
(2.3 legs). 




DECADE RESISTOR BOX 

Range. 100 ohms to I I 1.000 ohms. 

Zero Resistance: 0.006 ohms. 

Accuracy: ■ |%, 

Maximum current: 10's decade 100 mA. 

100's decade 35 mA. 1,000's decade 

10 mA. 

Terminals: Screw type. 

Dimensions (overall): Height 3 in. 

(7,5 cms). Width 8 in. (20 cms). Depth 

3| in. (9.5 cms.) Weight 5 lbs. (2.3 kgs). 



V > \ » . \% 

o ir . o . io o io 



SEMI-DECADE OSCILLATOR 




Frequency range. lOc.s.to 100 Kcs. Cali- 
bration accuracy I";,. 
Output. Sine wave variable from 0-10 v 
peak. Total content of harmonics and 
hum is less than 1%, Square wave of 
fixed amplitude of 10 v 5"„ maximum 
drop at lOeps is 2"„. The rise and fall 
time at 100 Kcs. is I Micro sec. 
Amplitude Stibility: Output stability 

I ",, at any frequency. 
Frequency Stability: Better than I "„. 
Power Supply: 100 120 v. 200-250 v, 
50 60 cycles. 

Terminals. Concentric sockets for sine 
and square wave outputs. 
Accessories supplied: Mains lead. Co- 
axial Output Plug, 



Telephone 

Walton-on-Tnames 

2632115 



WINSTON 



L 



ELECTRONICS LIMITED 



GOVETT AVENUE • SHEPPERTON 



Telegrams : 

WINSTON 

SHEPPERTON 



HJDDX. 



L><»1> 



whenever 



quality 




counts 



..t|iitili(> of sound reproduction 
or i|iialit,v of television pJetara, Brinw 

valves have a vilul part to play. 
Distortion-free amplifieation largely 
depends on having the right valve . . . ami 
Brimar Valves have proved conclusively lo lie 
tin- tight ralTOB for today's- exacting necils. 
When it comes to TV. Brhnar Teletnhes 
are ei|iinlly 'in the picture'. No wonder 
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IlliUlilliictiiri'rs anil I'm* drillers' 
replnrriiiriil purposes. 



better make It 



BRiviAR 



Standard Telephones and Cables Limited 



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STRONGLY RECOMMEND 

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OF REBUILT TUBE QUALITY 

Regular buyers of Pitrie Rebuilt Picture Tubes have learnt 
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PITRIE LIMITED 

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265 



CWS«I 



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392 COLLEGE HOUSE 
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COMPREHENSIVE 
TECHNICAL 
HANDBOOK SERVICE 

For complete data on 

Milliard Valves, Tubes, Semiconductors and Components 

The Milliard Technical Handbook is a loose-leaf 
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IMulLardl 

MULLARD LIMITED. 
T.S.D. DATA & PUBLICATIONS 
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TORRINGTON PLACE 
LONDON. W.C.I. 



_>r,ii 



287 




TECHNICALLY TRAINED by 



IN RADIO, TELEVISION AND 
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268 




TELEVISION 

TUBES 

REBUILT 



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introducing THE NEW SAPHIRE REBUILT TUBE 
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270 





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27a Howland Street, London Wl 
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271 




Ellay tllbeS featured in car aerials 

Ellay Small Diameter non-ferrous tubing plays a vital part ( CaDaCltOrS 

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tubular parts in non-ferrous metalstoyour specifications. 



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COX GREEN WORKS, MAIDENHEAD 
BERKS 

Tel: Maidenhead 3303 



272 



Other NEWNES books 
on television . . . 

RADIO & TELEVISION ENGINEERS' 
REFERENCE BOOK 

Editor: J. P. Hawker 

Advisory Editor: W. E. Pannett, A.M.i.E.E. 

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T.V. CONVERSION FOR I.T.A. 

by C. E. Lotcho 
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TELEVISION AND RADAR 
ENCYCLOPAEDIA 

Edited by W. MacLanachan 
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PRACTICAL TELEVISION CIRCUITS 

by F, J. Camm 
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TELEVISION PRINCIPLES AND 
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by F. J, Camm 
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INDUSTRIAL TELEVISION 

by H. A, McGhee, Grad. l.E.E. 
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A BEGINNER'S GUIDE TO 
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FROM ALL BOOKSELLERS 

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GEORGE NEWNES LTD. 

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THIS new book provides essentia! information and data 
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modern broadcast receivers. Special interest attaches 
to the fact that the new V.H.F.'F.M. models ar« dealt 
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The book includes more than 70 pages of tabular data, 
listing valve base connections, direct valve and battery equiv- 
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all B.B.C. and the major European medium and long-wave 
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GEORGE NEWNES LTD., Tower House, Southampton Street London, W.C.2 



RADIO 
SERVICING 
POCKET BOOK 

Edited by 

E. MOLLOY 

and 

J. P. HAWKER